**Exhibit
12.1**
 **CERTIFICATION
PURSUANT TO**
 **SECTION
302(a) OF THE SARBANES-OXLEY ACT OF 2002**
  I, Gad
Tamari, 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 registrant as of, and
for, the periods presented in this report;
  4. The
registrant’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(f)) for the registrant 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 registrant, 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;
  (c)
Evaluated the effectiveness of the registrant’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;
  (d)
Disclosed in this report any change in the registrant’s internal control over
financial reporting that occurred during the registrant’s most recent fiscal
quarter (the registrant’s fourth fiscal quarter in the case of an annual report)
that has materially affected, or is reasonably likely to materially affect, the
registrant’s internal control over financial reporting; and
  5. The
registrant’s other certifying officers and I have disclosed, based on our most
recent evaluation of internal control over financial reporting, to the
registrant’s auditors and the audit committee of the registrant’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 registrant’s ability to record, process, summarize and
report financial information; and
  (b) Any
fraud, whether or not material, that involves management or other employees who
have a significant role in the registrant’s internal control over financial
reporting.
  ****Date: April 5,
2005
    By:
    /s/ Gad Tamari*Gad TamariChief Executive
  Officer
  * The
originally executed copy of this Certification will be maintained at the
registrant’s offices and will be made available for inspection upon
request.