Table of Contents - Exhibits

Exbihit 12.1

CERTIFICATIONS

I,
Eduardo Vial, certify that:

|1. |  | I
have reviewed this annual report on Form 20-F of Masisa S.A.;
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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 company as of, and for, the
periods presented in this report;
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|4. |  | The
companys other certifying officer(s) 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:
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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 company, 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) | Evaluated
the effectiveness of the company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
| | --- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| | (c) | 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
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|5. |  | The
companys other certifying officer(s) 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 the company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
                                    companys ability to record, process, summarize
and report financial information; and
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| | (b) | 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.
| | --- | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------

Date: June 30, 2004

| | /s/ Eduardo Vial       
| | -----------------------
| | Eduardo Vial           
| | Chief Executive Officer