Exhibit 31.1

CERTIFICATION

I, William P. Peters, Chairman and Chief Executive Officer, certify that:



| | 1. | I have reviewed this quarterly report on Form 10-Q of Adherex Technologies Inc. (the Company);
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| | 2. | Based on my knowledge, this quarterly 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 quarterly report;
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| | 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 Company as of, and for, the periods presented in this quarterly report;
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| | 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)) and internal control over the financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15(d)-15(f) 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 quarterly 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;
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| | (c) | Evaluated the effectiveness of the Companys disclosure controls and procedures and presented in this quarterly report our conclusions about the effectiveness of the disclosure
controls and procedures, as of the end of the period covered by this quarterly report based on such evaluation; and
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| | (d) | Disclosed in this quarterly report any change in the Companys internal control over financial reporting that occurred during the
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| | period covered by the quarterly 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 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):
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| | (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.
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Date: May 14, 2007



By:

/s/ William P. PetersWilliam P. PetersChairman and Chief Executive Officer