The 2008–09 UEFA Champions League group stage matches took place between 16 September and 10 December 2008.

Seeding structure

Seeding was determined by the UEFA coefficients: Pot 1 held teams ranked 1–10 (since Milan and Sevilla did not qualify), Pot 2 held teams ranked 11–23, Pot 3 held teams ranked 25–45, while Pot 4 held teams ranked 46–193 and unranked teams. Clubs from the same association were paired up to split the matchdays between Tuesday and Wednesday. Clubs with the same pairing letter played on different days, ensuring that teams from the same city (e.g. Milan and Internazionale, who also share a stadium) did not play on the same day. Of the 16 teams in Pots 1 and 2, 14 eventually qualified for the first knockout round. The exceptions were Werder Bremen (to the UEFA Cup) and PSV Eindhoven (eliminated). Their places went to Panathinaikos (from Pot 3) and Atlético Madrid (from Pot 4). AaB were the lowest-ranked Pot 4 team to qualify for the UEFA Cup Round of 32.

Tie-breaking criteria

Based on paragraph 6.05 in the UEFA regulations for the current season, if two or more teams were equal on points on completion of the group matches, the following criteria were applied to determine the rankings:

Groups

Times are CET/CEST, as listed by UEFA (local times are in parentheses).

Group A

Group B

Group C

Group D

Group E

Group F

Group G

Group H