<PAGE>   1


                       SECURITIES AND EXCHANGE COMMISSION

                             Washington, D.C. 20549

                                    FORM 10-Q

                  QUARTERLY REPORT UNDER SECTION 13 OR 15(d) OF
                       THE SECURITIES EXCHANGE ACT OF 1934


For quarter ended September 30, 1997              Commission File Number 0-13147
                  ------------------                                     -------

                                   LESCO, INC.
-------------------------------------------------------------------------------
             (Exact name of registrant as specified in its charter)

       OHIO                                                34-0904517
------------------------------                  --------------------------------
State or other jurisdiction of                  (I.R.S. Employer Identification
incorporation or organization)                   Number)         

           20005 Lake Road
           Rocky River, Ohio                                 44116
----------------------------------------                  ----------
(Address of principal executive offices)                  (Zip Code)


                                 (216) 333-9250
                         -------------------------------
                         (Registrant's telephone number,
                              including area code)


Indicate by check mark whether the registrant (1) has filed all reports required
to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during
the preceding twelve months (or for such shorter period that the registrant was
required to file such reports), and (2) has been subject to such filing
requirements for the past 90 days. Yes  X    No
                                      -----    -----


Indicate the number of shares outstanding of each of the issuer's classes of
common stock, as of the close of the latest practical date.

                                                             Outstanding at
                 Class                                      November 11, 1997
     ------------------------------                        -----------------
    Common shares, without par value                         8,254,934 shares





<PAGE>   2
<TABLE>
<CAPTION>


                                                                     LESCO, INC.
                                                             CONSOLIDATED BALANCE SHEETS




                                                                        September 30        September 30        December 31
(In Thousands Except Share Data)                                             1997               1996               1996
                                                                        ------------        ------------        -----------
                                                                                         (unaudited)
ASSETS
<S>                                                                     <C>                 <C>                 <C>        
CURRENT ASSETS
     Cash                                                               $     5,828         $     5,298         $     1,900
     Accounts receivable -- net                                              75,202              69,269              57,424
     Inventories                                                             82,335              75,640              68,090
     Deferred income taxes                                                    4,760               1,194               4,734
     Prepaid expenses and other assets                                        1,822               1,842               4,398
                                                                        -----------         -----------         -----------
         TOTAL CURRENT ASSETS                                               169,947             153,243             136,546

Property, plant and equipment                                                56,050              46,054              47,747
     Less allowance for depreciation and amortization                       (28,638)            (23,738)            (24,454)
                                                                        -----------         -----------         -----------
                                                                             27,412              22,316              23,293

Other Assets                                                                  4,714               4,748               4,834
                                                                        -----------         -----------         -----------

         TOTAL ASSETS                                                   $   202,073         $   180,307         $   164,673
                                                                        ===========         ===========         ===========

LIABILITIES AND SHAREHOLDERS' EQUITY

CURRENT LIABILITIES:
     Accounts payable                                                   $    42,152         $    39,362         $    26,786
     Other current liabilities                                               10,332               9,878               9,656
     Current portion of long-term debt                                          200                 200                 200
                                                                        -----------         -----------         -----------
         TOTAL CURRENT LIABILITIES                                           52,684              49,440              36,642

Long-term debt                                                               75,098              59,441              64,704
Deferred income taxes                                                         1,627               1,132               1,628

SHAREHOLDERS' EQUITY:
     Preferred shares-- without par value--
         authorized 500,000 shares
     Common shares--without par value--
         19,500,000 shares authorized;  8,250,734 shares issued
         and 8,247,584 outstanding at September 30, 1997, 8,019,338
         at September 30, 1996, 8,064,367 at December 31, 1996                  825                 802                 807
     Paid-in capital                                                         28,758              25,822              26,549
     Retained earnings                                                       43,432              43,687              34,694
     Less treasury shares                                                       (17)                (17)                (17)
     Unearned compensation                                                     (334)                                   (334)
                                                                        -----------         -----------         -----------

         TOTAL SHAREHOLDERS' EQUITY                                          72,664              70,294              61,699
                                                                        -----------         -----------         -----------

         TOTAL LIABILITIES AND
         SHAREHOLDERS' EQUITY                                           $   202,073         $   180,307         $   164,673
                                                                        ===========         ===========         ===========


</TABLE>

                                       2

<PAGE>   3
<TABLE>
<CAPTION>




                                                                                LESCO, INC.
                                                               CONSOLIDATED STATEMENTS OF INCOME (unaudited)

                                                   Three Months Ended September 30           Nine Months Ended September 30
                                                  --------------------------------          --------------------------------

     (In Thousands, Except per Share Data)            1997                 1996                 1997                 1996
                                                   ---------           ----------           ----------            ----------

<S>                                                <C>                  <C>                  <C>                  <C>      
Net sales                                          $ 103,244            $  91,316            $ 279,638            $ 249,293

Cost of sales                                         69,313               62,069              186,661              168,954
                                                   ---------            ---------            ---------            ---------

     GROSS PROFIT ON SALES                            33,931               29,247               92,977               80,339

Selling, general and
     administrative expenses                          26,757               23,312               75,850               68,652
                                                   ---------            ---------            ---------            ---------

     INCOME FROM OPERATIONS                            7,174                5,935               17,127               11,687

Other deductions (income):
     Interest expense                                  1,122                1,012                3,446                3,089
     Other - net                                      (1,234)                (981)              (2,238)              (2,295)
                                                   ---------            ---------            ---------            ---------
                                                        (112)                  31                1,208                  794
                                                   ---------            ---------            ---------            ---------

Income before income taxes                             7,286                5,904               15,919               10,893

Income taxes                                           2,842                2,303                6,209                4,249
                                                   ---------            ---------            ---------            ---------


     NET INCOME                                    $   4,444            $   3,601            $   9,710            $   6,644
                                                   =========            =========            =========            =========



     EARNINGS PER SHARE                            $    0.52            $    0.43            $    1.15            $    0.81
                                                   =========            =========            =========            =========

Weighted average number of
     common and common equivalent
     shares outstanding                                8,624                8,279                8,411                8,239
                                                   =========            =========            =========            =========
</TABLE>




                                       3
<PAGE>   4

<TABLE>
<CAPTION>






                                                            LESCO, INC.
                                          CONSOLIDATED STATEMENTS OF CASH FLOW (unaudited)


                                                                                            Nine Months Ended
                                                                                              September 30
                                                                                 ----------------------------------
(In Thousands)                                                                      1997                     1996
                                                                                 ----------               ---------
<S>                                                                               <C>                      <C>     
OPERATING ACTIVITIES:
     Net income                                                                   $  9,710                 $  6,644
     Adjustments to reconcile net income to net cash
         provided  by operating activities:
         Depreciation and amortization                                               3,131                    2,597
         Increase in accounts receivable                                           (18,188)                 (22,651)
         Provision for uncollectible accounts receivable                             1,478                    1,104
         Increase in inventories                                                   (13,784)                  (7,795)
         Increase in accounts payable                                               14,520                   15,692
         Increase in other current items                                             3,245                    5,573
         Other                                                                         313                      130
                                                                                  --------                 --------

     NET CASH PROVIDED IN OPERATING ACTIVITIES                                         425                    1,294

INVESTING ACTIVITIES:
     Purchase of property, plant and equipment                                      (4,934)                  (3,257)
     Acquisition of businesses (net of $18 cash received)                           (2,949)                 (11,268)
                                                                                  --------                 --------

     NET CASH USED BY INVESTING ACTIVITIES                                          (7,883)                 (14,525)

FINANCING ACTIVITIES:
     Proceeds from borrowings                                                       80,514                   79,500
     Reduction of borrowings                                                       (70,120)                 (63,317)
     Issuance of common shares                                                       1,965                      605
     Cash dividends                                                                   (973)                    (879)
                                                                                  --------                 --------

     NET CASH PROVIDED BY FINANCING ACTIVITIES                                      11,386                   15,909
                                                                                  --------                 --------

Net Increase in Cash                                                                 3,928                    2,678

Cash --  Beginning of the Period                                                     1,900                    2,620
                                                                                  --------                 --------

     CASH - END OF THE PERIOD                                                     $  5,828                 $  5,298
                                                                                  ========                 ========


</TABLE>


                                       4








<PAGE>   5






                                   LESCO, INC.
                          NOTES TO FINANCIAL STATEMENTS
                          -----------------------------


NOTE A - Basis of Presentation
------------------------------

The accompanying unaudited financial statements have been prepared in accordance
with generally accepted accounting principles for interim financial information
and with the requirements of Regulation S-X and Form 10-Q. The statements
reflect all adjustments, consisting only of normal recurring accruals, which
are, in the opinion of management, necessary for a fair presentation of the
results for interim periods. For further information, refer to the audited
financial statements and footnotes thereto for the year ended December 31, 1996
included in the Company's Form 10-K.

Operating results for the nine months ended September 30 are not necessarily
indicative of the results to be expected for the year due to the seasonal nature
of the Company's business.

NOTE B - Acquisition of Tri Delta Fertilizer, Inc.
--------------------------------------------------

On August 1, 1997, the Company purchased all of the outstanding shares of Tri
Delta Fertilizer, Inc. for $3.2 million consisting of $2.9 million in cash and
the issuance of 12,465 shares of the Company's common stock. Tri Delta, located
in Stockton, California, is a manufacturer and distributor of granular and
liquid fertilizer and combination products to customers in the turf care and
agricultural markets throughout the western United States. The Company recorded
the acquisition using the purchase method of accounting and Tri Delta operations
since August 1, 1997 are included in the Company's consolidated financial
statements.







                                       5
<PAGE>   6





                                   LESCO, INC.
                  FINANCIAL CONDITION AND RESULTS OF OPERATIONS
                      MANAGEMENT'S DISCUSSION AND ANALYSIS
                      ------------------------------------


Results of Operations
---------------------


For the third quarter ended September 30, 1997 sales increased 13.1% to $103.2
million from $91.3 million in 1996. Sales for the first nine months of 1997
increased 12.2% to $279.6 million from $249.3 million in 1996. Both consumable
and hard good sales volume increased in the third quarter and the first nine
months of 1997 compared to 1996. Sales increases for both the third quarter and
the first nine months reflect the increase of Service Centers in operation to
215 as of September 30, 1997 from 196 in operation as of January 1997. Same
store sales for the third quarter and first nine months of 1997 compared to 1996
increased 10.7% and 12.7%, respectively. The Company has concluded its 1997
Service Center expansion program and is planning an expansion of a similar
number of stores in 1998.

Gross profit as a percent of sales was 32.9% in the third quarter 1997 compared
to 32.0% in 1996 with the first nine months gross profit as a percent of sales
in 1997 being 33.2% compared to 32.2% in 1996. The gross profit percentage
increase occurred in both the consumable and hard goods for both the quarter and
year-to-date. The Company continues to focus on margin improvements through
refinements in product purchases and enhancements in sales pricing strategies.

The Company's selling, general and administrative expenses increased $3.4
million, a 14.8% increase to $26.7 million for the third quarter 1997 compared
to $23.3 million in the third quarter 1996. Selling, general and administrative
expenses increased $7.2 million, a 10.5% increase to $75.9 million for the first
nine months 1997 compared to $68.7 million in the first nine months 1996.
Service Center and delivery expenses contributed the largest dollar increase in
selling, general and administrative expenses in the third quarter and the first
nine months of 1997 compared to 1996. Service Center expenses are up due to the
increase in the number of Service Centers in operation. The increase in delivery
expense is a result of the increase in sales volume and a change in product mix
weighted more towards fertilizer and combination products.

Interest expense was $1,122,000 in the third quarter 1997 compared to $1,012,000
in 1996 and $3,446,000 year-to-date 1997 compared to $3,089,000 in 1996. This
increase is primarily due to increased borrowings for working capital
requirements for sales expansion and the acquisition of Tri Delta Fertilizer,
Inc.. Other deductions-net include customer finance charges which total
$1,115,000 for the third quarter 1997 compared to $938,000 in 1996 and
$2,281,000 year-to-date 1997 compared to $2,125,000 in 1996.



                                       6

<PAGE>   7




Financial Condition, Liquidity and Capital Resources
----------------------------------------------------

As of September 30, 1997, total assets of the Company were $202.1 million
compared to $180.3 million as of September 30, 1996 and $164.7 million as of
December 31, 1996. The asset increase from September 30, 1997 to September 30,
1996 is primarily related to working capital increases resulting from increased
sales volume while the increase from December 31, 1996 is due to the seasonality
of the business. Accounts receivable were $75.2 million as of September 30, 1997
compared to $69.3 million as of September 30, 1996, an 8.6 % increase due
primarily to the increase in sales, and $57.4 million as of December 31, 1996.
Inventories were $82.3 million as of September 30, 1997 compared to $75.6
million as of September 30, 1996, an 8.9% increase also due to sales increases,
and $68.1 million as of December 31, 1996.

Funding was provided primarily by an increase in long-term debt along with an
increase in accounts payable. The Company's long-term debt increased to $75.1
million as of September 30, 1997 through additional borrowings under the
Company's credit facility. Accounts payable increased to $42.2 million as of
September 30, 1997 from $39.4 million as of September 30, 1996 and $26.8 million
as of December 31, 1996. The increase from September 30, 1996 relates to the
increases in inventories as noted above while the increase from December 31,
1996 is primarily related to seasonality.

Outstanding debt under the Company's credit facility was $68.7 million as of
September 30, 1997 compared to $52.9 million as of September 30, 1996 and $58.2
million as of December 31, 1996. As of September 30, 1997 the Company had $11.3
million available under its credit facility.

Capital expenditures for the first nine months of 1997 totaled $4.9 million and
relate primarily to the opening of Service Centers, improvements in the
Company's information systems and the construction of the Company's new
fertilizer plant in Sebring, Florida.







New Accounting Requirements
---------------------------

The new requirements for calculating earnings per share under Financial
Accounting Standards Board Statement #128, Earnings Per Share, will be effective
December 31, 1997. Management does not expect the impact of adopting the
statement to have a material impact on earnings per share.

In June 1997, the Financial Accounting Standards Board issued FAS No. 131,
"Disclosures about Segments of an Enterprise and Related Information". The
statement requires a "management" approach to reporting financial and
descriptive information about a Company's operating segments. The Company must
adopt this statement in the first quarter of fiscal 1998. Management is
currently studying the potential effect of adopting this statement.




                                       7
<PAGE>   8


                           PART II - OTHER INFORMATION
                           ---------------------------

Except as noted below, the items in Part II are inapplicable or, if applicable,
would be answered in the negative. These items have been omitted and no other
reference is made thereto.




Item 6 - Exhibits and Reports on Form 8-K
-----------------------------------------

         (a)      Exhibits:
                  (27) Financial Data Schedule












                                       8
<PAGE>   9





                                   SIGNATURES
                                   ----------

                  Pursuant to the requirements of the Securities Exchange Act of
1934, the registrant has duly caused this report to be signed on its behalf by
the undersigned thereunto duly authorized.

                                            LESCO, INC.





November 11, 1997                           By: /s/ Ware H. Grove
-------------------                         ----------------------------------
                                            Ware H. Grove, Vice-President/
                                                     Chief Financial Officer










                                       9