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Exhibit 31.1 Certification of the President and Chief Executive Officer
Pursuant to Section 302 of the Sarbanes-Oxley Act of 2002 I, Brian Ainsworth, certify that:  1.
    
    I have reviewed this report on Form 20-F of Ainsworth Lumber Co.
Ltd.;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 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:  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;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; andc.
    
    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 the companys board of
directors (or persons performing the equivalent function):  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; andb.
    
    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: May 21, 2004
    
    By:
    
    /s/ Brian Ainsworth
Brian Ainsworth
Chief Executive Officer
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Exhibit 31.1 Certification of the President and Chief Financial Officer
Pursuant to Section 302 of the Sarbanes-Oxley Act of 2002 I, Robert Allen, certify that:  1.
    
    I have reviewed this report on Form 20-F of Ainsworth Lumber Co.
Ltd.;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 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:  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;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; andc.
    
    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 the companys board of
directors (or persons performing the equivalent function):  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; andb.
    
    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: May 21, 2004
    
    By:
    
    /s/ Robert Allen
Robert Allen
Chief Financial Officer
 66