**Exhibit 31.2**

**Certification of PrincipalFinancial Officer Required by Rule 13a-14(a) or 15d-14(a)of the Securities Exchange Act of 1934**

I, David W. Montgomery, certify that:

(1)         I havereviewed this report on Form 10-Q of Advanstar, Inc. (the “registrant”);

(2)         Based onmy knowledge, this report does not contain any untrue statement of a materialfact or omit to state a material fact necessary to make the statements made, inlight of the circumstances under which such statements were made, notmisleading with respect to the period covered by this report;

(3)         Based on my knowledge, the financial statements, and other financialinformation included in this report, fairly present in all material respectsthe financial condition, results of operations and cash flows of the registrantas of, and for, the periods presented in this report;

(4)         The registrant’s othercertifying officer and I are responsible for establishing and maintainingdisclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and15d-15(e)) for the registrant and we have:

(a)           Designed suchdisclosure controls and procedures, or caused such disclosure controls andprocedures to be designed under our supervision, to ensure that materialinformation relating to the registrant, including its consolidatedsubsidiaries, is made known to us by others within those entities, particularlyduring the period in which this report is being prepared;

(b)          [Reserved]

(c)           Evaluated theeffectiveness of the registrant’s disclosure controls and procedures andpresented in this report our conclusions about the effectiveness of thedisclosure controls and procedures, as of the end of the period covered by thisreport based on such evaluation; and

(d)          Disclosed in this reportany change in the registrant’s internal control over financial reporting thatoccurred during the registrant’s most recent fiscal quarter (the registrant’sfourth fiscal quarter in the case of an annual report) that has materiallyaffected, or is reasonably likely to materially affect, the registrant’sinternal control over financial reporting;

(5)         The registrant’s othercertifying officer and I have disclosed, based on our most recent evaluation ofinternal control over financial reporting, to the registrant’s auditors and theaudit committee of the registrant’s board of directors (or persons performingthe equivalent functions):

(a)           All significantdeficiencies and material weaknesses in the design or operation of internalcontrol over financial reporting which are reasonably likely to adverselyaffect the registrant’s ability to record, process, summarize and reportfinancial information; and

(b)          Anyfraud, whether or not material, that involves management or other employees whohave a significant role in the registrant’s internal control over financialreporting.
| Date: November 15, 2004 |   |   |                                |
|------------------------------|--------|--------|-------------------------------------|
|                         | By:    |   | /s/  DAVID  W. MONTGOMERY |
|                         |   |   | David W. Montgomery                 |
|                         |   |   | *Chief Financial Officer*           |

 

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