**Exhibit 31.1**

 

**Section 302Certification**

 

I,Daniel M. Quinn, certify that:

 
| 1.     | I have reviewed this  report on Form 10-Q for the quarter ended June 30, 2009, of  Guaranty Bancorp;                                                                                                                                                                                                                                                                                                   |
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| 2.     | Based on my knowledge,  this report does not contain any untrue statement of a material fact or omit  to state a material fact necessary to make the statements made, in light of  the circumstances under which such statements were made, not misleading with  respect to the period covered by this report;                                                                                                   |
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| 3.     | Based on my knowledge,  the financial statements, and other financial information included in this  report, fairly present in all material respects the financial condition,  results of operations and cash flows of the registrant as of, and for, the  periods presented in this report;                                                                                                                      |
|   |                                                                                                                                                                                                                                                                                                                                                                                                             |
| 4.     | The registrant’s other  certifying officer and I are responsible for establishing and maintaining  disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and  15d-15(e)) and internal control over financial reporting (as defined in  Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and  have:                                               |
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| (a)    | Designed such  disclosure controls and procedures, or caused such disclosure controls and  procedures to be designed under our supervision, to ensure that material  information relating to the registrant, including its consolidated  subsidiaries, is made known to us by others within those entities,  particularly during the period in which this report is being prepared;                              |
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| (b)    | Designed such internal  control over financial reporting, or caused such internal control over  financial reporting to be designed under our supervision, to provide  reasonable assurance regarding the reliability of financial reporting and the  preparation of financial statements for external purposes in accordance with  generally accepted accounting principles;                                     |
|   |                                                                                                                                                                                                                                                                                                                                                                                                             |
| (c)    | Evaluated the  effectiveness of the registrant’s disclosure controls and procedures and  presented in this report our conclusions about the effectiveness of the  disclosure controls and procedures, as of the end of the period covered by  this report based on such evaluation; and                                                                                                                     |
|   |                                                                                                                                                                                                                                                                                                                                                                                                             |
| (d)    | Disclosed in this  report any change in the registrant’s internal control over financial  reporting that occurred during the registrant’s most recent fiscal quarter  (the registrant’s fourth fiscal quarter in the case of an annual report) that  has materially affected, or is reasonably likely to materially affect, the  registrant’s internal control over financial reporting; and |
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| 5.     | The registrant’s other  certifying officer and I have disclosed, based on our most recent evaluation  of internal control over financial reporting, to the registrant’s auditors  and the audit committee of the registrant’s board of directors (or persons  performing the equivalent functions):                                                                                               |
|   |                                                                                                                                                                                                                                                                                                                                                                                                             |
| (a)    | All significant  deficiencies and material weaknesses in the design or operation of internal  control over financial reporting which are reasonably likely to adversely  affect the registrant’s ability to record, process, summarize and report  financial information; and                                                                                                                               |
|   |                                                                                                                                                                                                                                                                                                                                                                                                             |
| (b)    | Any fraud, whether or  not material, that involves management or other employees who have a  significant role in the registrant’s internal control over financial  reporting.                                                                                                                                                                                                                               |
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Date:July 31, 2009

 

 
|     | /s/   Daniel M. Quinn     |
|----------|------------------------------------------|
|     | Daniel M. Quinn                          |
| * * | *President  and Chief Executive Officer* |

 

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