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Exhibit 12.1

# CERTIFICATION OF CHIEF
EXECUTIVE OFFICER Pursuant to Rule
13a-14(a) under the Securities Exchange Act of 1934, as amended

I, Boaz Raviv, certify
that:

|1. | I
have reviewed this annual report on Form 20-F of RADVISION Ltd.;
|-- | ------------------------------------------------------------------

|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;
|-- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

|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;
|-- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

|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 financial           reporting
(as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) 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) | 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 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
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| | (d) | 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;
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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 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; 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: March 25, 2009

/s/ Boaz Raviv*
Boaz Raviv
Chief Executive Officer

*     The
originally executed copy of this Certification will be maintained at the companys
offices and will be made available for inspection upon request.



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