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                                                                    EXHIBIT 12.1

                                 CERTIFICATIONS

                    CERTIFICATION OF CHIEF EXECUTIVE OFFICER

      I, Rene Sagastuy, certify that:

      1. I have reviewed this annual report on Form 20-F of Maxcom
Telecomunicaciones, S.A. de C.V.;

      2 Based on my knowledge, this annual 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 annual
report;

      3. Based on my knowledge, the financial statements, and other financial
information included in this annual report, fairly present in all material
respects the financial condition, results of operations and cash flows of the
company as of, and for, the periods presented in this annual report;

      4. The company'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)) for the company and have:

      (i)   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
            company, including its consolidated subsidiaries, is made known to
            us by others within those entities, particularly during the period
            in which this annual report is being prepared;

      (ii)  evaluated the effectiveness of the company's disclosure controls and
            procedures and presented in this annual report our conclusions about
            the effectiveness of the disclosure controls and procedures as of
            the period covered by this report based on such evaluation; and

      (iii) disclosed in this report any change in the company's internal
            control over financial reporting that occurred during the period
            covered by the annual report that has materially affected, or is
            reasonably likely to materially affect, the company's internal
            control over financial reporting; and

      5. The company's other certifying officer and I have disclosed, based on
our most recent evaluation of internal control over financial reporting, to the
company's auditors and the audit committee of company's board of directors (or
persons performing the equivalent function):

      (i)   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 company's ability to
            record, process, summarize and report financial information; and

      (ii)  any fraud, whether or not material, that involves management or
            other employees who have a significant role in the company's
            internal control over financial reporting.

                                                 /s/ RENE SAGASTUY
                                                 ------------------------------
                                                 Rene Sagastuy
                                                 Chief Executive Officer

Dated:  June 29, 2006