Exhibit 99.1

                                  CERTIFICATION

                Pursuant to Section 906 of the Sarbanes-Oxley Act
         of 2002 (Subsections (a) and (b) of Section 1350, Chapter 63 of
                          Title 18, United States Code)

         Pursuant to section 906 of the Sarbanes-Oxley Act of 2002 (subsections
(a) and (b) of section 1350, chapter 63 of title 18, United States Code), each
of the undersigned officers of deltathree, Inc., a Delaware corporation (the
"Company"), does hereby certify, to such officer's knowledge, that:

         The Quarterly Report on Form 10-Q for the quarter ended September 30,
2002 (the "Form 10-Q") of the Company fully complies with the requirements of
section 13(a) or 15(d) of the Securities Exchange Act of 1934, and information
contained in the Form 10-Q fairly presents, in all material respects, the
financial condition and results of operations of the Company.


Dated:   November 14, 2002          /s/Shimmy Zimels
         -----------------          ----------------
                                    Shimmy Zimels
                                    Chief Executive Officer
                                    (Principal Executive Officer)


Dated:   November 14, 2002          /s/Paul C. White
         -----------------          ----------------
                                    Paul C. White
                                    Chief Financial Officer
                                    (Principal Financial and Accounting Officer)



         This certification accompanies this Report pursuant to ss. 906 of the
Sarbanes-Oxley Act of 2002 and shall not, except to the extent required by the
Sarbanes-Oxley Act of 2002, be deemed filed by the Company for purposes of ss.
18 of the Securities Exchange Act of 1934, as amended.