Exhibit 31.1



CERTIFICATIONS



Chief Executive
Officer Certification pursuant to

Section 302 of the Sarbanes-Oxley Act of 2002



I, Ricardo A. Verdaguer, certify that:



1. I have reviewed this quarterly report on Form 10-Q of IMPSAT Fiber Networks, Inc. (the
Registrant);



2. Based on my knowledge, this quarterly report does
not contain any untrue statement of a material fact or omit to state 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
quarterly report;



3. Based on my knowledge, the financial statements, and
other financial information included in this quarterly 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 quarterly report;



4. The Registrants other certifying officer and I are responsible for
establishing and maintaining disclosure controls and procedures (as defined in the Securities and Exchange Act of 1934 Rules 13a-15(e) and 15d-15(e)) for the Registrant and we have:



(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,



(b) [omitted pursuant to the guidance of Release No. 33-8283
(June 5, 2003)],



(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



5. The Registrants other certifying officer and I have disclosed, based on our most recent evaluation, to the Registrants auditors and the audit committee of the Registrants board of directors (or
persons performing the equivalent function):



(a) all
adversely significant deficiencies and material weaknesses in the design or operation of internal controls over financial reporting which are reasonably likely to 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 controls over financial reporting.



| |  |                                      
| |  | -------------------------------------
| |  | /s/ Ricardo A. Verdaguer             
| |  | Ricardo A. Verdaguer                 
| |  | President and Chief Executive Officer



May
23, 2005