<Page> EXHIBIT 12.3 VIDEOTRON LTEE COMPUTATION OF RATIO OF EBITDA TO CASH INTEREST EXPENSE (DOLLARS IN MILLIONS, EXCEPT FOR RATIO OF EBITDA TO CASH INTEREST EXPENSE) <Table> <Caption> YEAR ENDED SIX MONTHS DECEMBER 31, ENDED JUNE 30, ------------------------------ ------------------- 2002 2003 2004 2004 2005 -------- -------- -------- -------- -------- CANADIAN GAAP EBITDA(1)................................................ $210.4 $277.7 $341.1 $163.7 $187.5 Cash interest expense(2)................................. 76.4 65.1 59.4 30.2 30.1 ------ ------ ------ ------ ------ Ratio of EBITDA to cash interest expense................. 2.8 4.3 5.7 5.4 6.2 ------ ------ ------ ------ ------ </Table> - --------- (1) As defined and calculated in note 7 to "Selected Consolidated Financial and Operating Data." (2) As defined and calculated in note 9 to "Selected Consolidated Financial and Operating Data."