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                                                                    EXHIBIT 12.1

             CERTIFICATION OF CHIEF EXECUTIVE OFFICER OR EQUIVALENT

I, SOON-YUB SAMUEL KWON, certify that:

      1.    I have reviewed this annual report on Form 20-F of Korea Thrunet
            Co., Ltd. (the "Company");

      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)   [Omitted pursuant to the guidance of Release No. 33-8238
                        (June 5, 2003), Release No. 33-8392 (February 2, 2004)
                        and Release No. 33-8545 (March 2, 2005)];

                  (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

                  (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; 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
            functions):

                  (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

                  (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.

Date: July 15, 2005

/s/ Soon-Yub Samuel Kwon
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Soon-Yub Samuel Kwon
Chief Executive Officer