Exhibit 99.3

March 9, 2011

Mr. Andrew R. Agosto

Vice President

Carrizo Oil & Gas, Inc.

1000 Louisiana Street, Suite 1500

Houston, Texas 77002

Dear Mr. Agosto:

At your request, LaRoche Petroleum Consultants, Ltd. (LPC) has estimated the proved reserves and future cash flow, as of
December 31, 2010, to the Carrizo Oil & Gas, Inc. (Carrizo) interest in certain properties located in Denton, Erath, Hill, Hood, Jack, Johnson, Parker, Tarrant and Wise counties, Texas. This report was completed as of the date of this
letter. This report was prepared to provide Carrizo with Securities and Exchange Commission (SEC) compliant reserve estimates. It is our understanding that the properties evaluated by LPC comprise eighty percent (80%) of Carrizos total
proved reserves. We believe that the assumptions, data, methods, and procedures used in preparing this report, as set out below, are appropriate for the purpose of this report. This report has been prepared using constant prices and costs and
conforms to our understanding of the SEC guidelines, reserves definitions, and applicable financial accounting rules.

Summarized below are LPCs estimates of net reserves and future net cash flow. Future net revenue is prior to deducting estimated
production and ad valorem taxes. Future net cash flow is after deducting these taxes, operating expenses, and future capital expenditures but before consideration of federal income taxes. The discounted cash flow values included in this report are
intended to represent the time value of money and should not be construed to represent an estimate of fair market value. We estimate the net reserves and future net cash flow to the Carrizo interest, as of December 31, 2010, to be:



|                   |  |              |         |  |                           |  |           |          |  |  |             |  |  |                     |               |  |  |   |             | 
|------------------ |  | ------------ | ------- |  | ------------------------- |  | --------- | -------- |  |  | ----------- |  |  | ------------------- | ------------- |  |  | - | ----------- | 
|                   |  | Net Reserves |         |  | Future Net Cash Flow (M$) | 
|Category           |  | Oil(Barrels) |         |  | NGL(Barrels)              |  |           | Gas(Mcf) |  |  | Total       |  |  | Present Worth at10% |              
|Proved Developed   |  |              |         |  |                           |  |           |          |  |  |             |  |  |                     |               |  |  |   |             | 
|Producing          |  |              | 77,704  |  |                           |  | 3,845,129 |          |  |  | 322,785,250 |  |  | $                   | 814,331,375   |  |  | $ | 401,275,125 | 
|Non-Producing      |  |              | 0       |  |                           |  | 0         |          |  |  | 22,132,504  |  |  | $                   | 55,705,836    |  |  | $ | 27,815,941  | 
|Proved Undeveloped |  |              | 133,656 |  |                           |  | 4,968,647 |          |  |  | 280,819,562 |  |  | $                   | 514,580,562   |  |  | $ | 117,869,219 | 
|                   |  |              |         |  |                           |  |           |          |  |  |             |  |  |                     |               |  |  |   |             | 
|                   |  |              |         |  |                          
|Total Proved(1)    |  |              | 211,360 |  |                           |  | 8,813,776 |          |  |  | 625,737,316 |  |  | $                   | 1,384,617,773 |  |  | $ | 546,960,285 | 



|1) | The total proved values above may or may not match those values on the total proved summary page that follows this letter due to rounding by the
economics program
|-- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------

The oil reserves include crude oil, condensate, and natural gas liquids (NGL). Oil and
NGL reserves are expressed in barrels, which are equivalent to 42 United States gallons. Gas reserves are expressed in thousands of standard cubic feet (Mcf) at the contract temperature and pressure bases.

The estimated reserves and future cash flow shown in this report are for proved developed producing reserves and, for certain properties,
proved developed non-producing and proved undeveloped reserves. This report does not include any value that could be attributed to



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interests in undeveloped acreage beyond those tracts for which undeveloped reserves have been estimated.

This report includes: (1) summary economic projections of reserves and cash flow for each reserve category, (2) one-line summaries of basic economic data and reserves for each property
evaluated, and (3) economic projections of reserves and cash flow for each evaluated property.

Estimates of reserves
were prepared using standard geological and engineering methods generally accepted by the petroleum industry. The reserves in this report have been estimated using deterministic methods. The method or combination of methods utilized in the
evaluation of each reservoir included consideration of the stage of development of the reservoir, quality and completeness of basic data, and production history. Recovery from various reservoirs and leases was estimated after consideration of the
type of energy inherent in the reservoirs, the structural positions of the properties, and reservoir and well performance. In some instances, comparisons were made to similar properties for which more complete data were available. We have used all
methods and procedures that we considered necessary under the circumstances to prepare this report. We have excluded from our consideration all matters as to which the controlling interpretation may be legal or accounting rather than engineering or
geoscience.

The estimated reserves and future cash flow amounts in this report are related to hydrocarbon prices. Historical
prices through December 2010 were used in the preparation of this report as required by SEC guidelines; however, actual future prices may vary significantly from the SEC prices. In addition, future changes in environmental and administrative
regulations may significantly affect the ability of Carrizo to produce oil and gas at the projected levels. Therefore, volumes of reserves actually recovered and amounts of cash flow actually received may differ significantly from the estimated
quantities presented in this report.

Benchmark prices used in this report are based on the twelve-month un-weighted
arithmetic average of the first day of the month price for the period January through December 2010. Gas prices are referenced to a WAHA physical price of $4.21 per MMBtu, as posted by Platts Daily Gas, and are adjusted for energy content,
transportation fees, and regional price differentials. Oil prices are referenced to a West Texas Intermediate (WTI) crude oil price of $76.05 per barrel, as posted by ConocoPhillips (Conoco), and are adjusted for gravity, crude quality,
transportation fees, and regional price differentials. NGL prices are calculated as a historical percentage of the WTI price and are referenced to a WTI physical price of $75.96 per barrel, as posted by Plains All American Pipeline, L.P. (Plains),
adjusted for transportation fees and regional price differentials. These reference prices are held constant in accordance with SEC guidelines. The weighted average prices over the life of the properties are $76.35 for oil, $3.432 for gas, and
$33.535 for NGL.

Lease and well operating expenses are based on data obtained from Carrizo. Expenses for the properties
operated by Carrizo include allocated overhead costs, direct lease and field level costs as well as compression costs and marketing expenses. Leases and wells operated by others include all direct expenses as well as general and administrative costs
and overhead costs allowed under the specific joint operating agreements. Costs for all properties have been divided into fixed field operating costs and variable per-well costs. Based on information supplied by Carrizo, gas gathering and
transportation costs are such that royalty interest owners assume their proportionate share of these costs. Lease and well operating costs are held constant in accordance with SEC guidelines.

Capital costs and timing of all investments have been provided by Carrizo and are included as required for workovers, new development
wells, and production equipment. Carrizo



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has represented to us that they have the ability and intent to implement their capital expenditure program as scheduled. Estimates of the cost to plug and abandon the wells net of salvage value
are included and scheduled at the end of the economic life of individual properties. These costs are held constant.

Severance
tax rates for all properties are calculated based on applicable State of Texas guidelines for High Cost Gas Exemption. Capital investments necessary to determine these severance tax rates have been provided by Carrizo.

LPC has made no investigation of possible gas volume and value imbalances that may have resulted from the overdelivery or underdelivery
to the Carrizo interest. Our projections are based on the Carrizo interest receiving its net revenue interest share of estimated future gross oil and gas production.

Technical information necessary for the preparation of the reserve estimates herein was furnished by Carrizo or was obtained from state regulatory agencies and commercially available data sources. No
special tests were obtained to assist in the preparation of this report. For the purpose of this report, the individual well test and production data as reported by the above sources were accepted as represented together with all other factual data
presented by Carrizo including the extent and character of the interest evaluated.

An on-site inspection of the properties
has not been performed nor has the mechanical operation or condition of the wells and their related facilities been examined by LPC. In addition, the costs associated with the continued operation of uneconomic properties are not reflected in the
cash flows.

The evaluation of potential environmental liability from the operation and abandonment of the properties is
beyond the scope of this report. In addition, no evaluation was made to determine the degree of operator compliance with current environmental rules, regulations, and reporting requirements. Therefore, no estimate of the potential economic
liability, if any, from environmental concerns is included in the projections presented herein.

The reserves included in this
report are estimates only and should not be construed as exact quantities. They may or may not be recovered; if recovered, the revenues therefrom and the costs related thereto could be more or less than the estimated amounts. These estimates should
be accepted with the understanding that future development, production history, changes in regulations, product prices, and operating expenses would probably cause us to make revisions in subsequent evaluations. A portion of these reserves are for
behind-pipe zones, undeveloped locations, and producing wells that lack sufficient production history to utilize performance-related reserve estimates. Therefore, these reserves are based on estimates of reservoir volumes and recovery efficiencies
along with analogies to similar production. These reserve estimates are subject to a greater degree of uncertainty than those based on substantial production and pressure data. It may be necessary to revise these estimates up or down in the future
as additional performance data become available. As in all aspects of oil and gas evaluation, there are uncertainties inherent in the interpretation of engineering and geological data; therefore, our conclusions represent informed professional
judgments only, not statements of fact.

The results of our third party study were prepared in accordance with the disclosure
requirements set forth in the SEC regulations and intended for public disclosure as an exhibit in filings made with the SEC by Carrizo.

Carrizo makes periodic filings on Form 10-K with the SEC under the 1934 Exchange Act. Furthermore, Carrizo has certain registration statements filed with the SEC under the 1933



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Securities Act into which any subsequently filed Form 10-K is incorporated by reference. We have consented to the incorporation by reference in the registration statements on Form S-3 and Form
S-8 of Carrizo of the references to our name, together with the references to our third party report for Carrizo which appears in the December 31, 2010 annual report on Form 10-K and/or 10-K/A of Carrizo. Our written consent for such use is
included as a separate exhibit to the filings made with the SEC by Carrizo.

We have provided Carrizo with a digital version
of the original signed copy of this report letter. In the event there are any differences between the digital version included in filings made by Carrizo and the original signed report letter, the original signed report letter shall control and
supersede the digital version.

The technical persons responsible for preparing the reserve estimates presented herein meet
the requirements regarding qualifications, independence, objectivity, and confidentiality set forth in the Standards Pertaining to the Estimating and Auditing of Oil and Gas Reserves Information promulgated by the Society of Petroleum Engineers. The
technical person primarily responsible for overseeing the preparation of reserves estimates herein is William M. Kazmann. Mr. Kazmann is a Professional Engineer licensed in the State of Texas who has thirty six years of engineering experience
in the oil and gas industry. Mr. Kazmann earned Bachelor of Science and Master of Science degrees in Petroleum Engineering from the University of Texas at Austin and has prepared reserves estimates for his employers and his own companies
throughout his career. He has prepared and overseen preparation of reports for public filings for LPC for the past fourteen years. LPC is an independent firm of petroleum engineers, geologists, and geophysicists and are not employed on a contingent
basis. Data pertinent to this report are maintained on file in our office.



Very truly yours,LaRoche Petroleum Consultants, Ltd.State of Texas Registration Number F-1360William M. KazmannLicensed Professional EngineerState of Texas No. 45012Al IakovakisManager of Unconventional Resource EvaluationsSenior Staff Engineer


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