Exhibit 31.2

Written Certification of Chief Financial Officer

I,Thomas A. Mutryn, certify that:

1.I have reviewed this quarterly report on Form 10-Q of GTSI Corp.;

2.Based on my knowledge, this report does not contain any untrue statement of amaterial fact or omit to state a material fact necessary to make the statementsmade, in light 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 financial informationincluded in this report, fairly present in all material respects the financialcondition, results of operations and cash flows of the registrant as of, andfor, the periods presented in this report;

4.The registrant’s other certifying officer and I are responsible forestablishing and maintaining disclosure controls and procedures (as defined inExchange Act Rules 13a-15(e) and 15d-15(e)) and internalcontrol over financial reporting (as defined in Exchange Act Rules 13a-15(f) and15d-15(f)), for the registrant and have:

a.             Designed such disclosure controls andprocedures, or caused such disclosure controls and procedures to be designedunder our supervision, to ensure that material information relating to theregistrant, including its consolidated subsidiaries, is made known to us byothers within those entities, particularly during the period in which thisreport is being prepared;

b.            Designed such internal control over financial reporting, or caused suchinternal control over financial reporting to be designed under our supervision,to provide reasonable assurance regarding the reliability of financialreporting and the preparation of financial statements for external purposes inaccordance with generally accepted accounting principles;

c.             Evaluated the effectiveness of the registrant’sdisclosure controls and procedures and presented in this report our conclusionsabout the effectiveness of the disclosure controls and procedures, as of theend of the period covered by this report based on such evaluation; and

d.            Disclosed in this report any change in the registrant’s internalcontrol over financial reporting that occurred during the registrant’s mostrecent fiscal quarter that has materially affected, or is reasonable likely tomaterially affect, the registrants’ internal control over financial reporting;and

5.The registrant’s other certifying officer and I have disclosed, based upon ourmost recent evaluation of internal control over financial reporting, to the registrants’auditors and the audit committee of the registrant’s board of directors:

a.             All significant deficiencies and materialweaknesses in the design or operation of internal control over financialreporting which are reasonably likely to adversely affect the registrant’sability to record, process, summarize and report financial information; and

b.            Any fraud, whether or not material, that involves management or otheremployees who have a significant role in the registrant’s internal control overfinancial reporting.

Date:       May 9, 2006
| /s/ THOMAS A. MUTRYN                               |   |
|----------------------------------------------------|--------|
| Thomas A. Mutryn                                   |   |
| Senior Vice  President and Chief Financial Officer |   |

 

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