2004 AFC Champions League

The 2004 AFC Champions League was the 23rd edition of the top-level Asian club football tournament and the 2nd edition under the current AFC Champions League title. The title was won by Al-Ittihad over Seongnam Ilhwa Chunma.

Format
A total of 28 clubs were divided into 7 groups of four, based on region i.e. East Asian and Southeast Asian clubs were drawn in groups E to G, while the rest were grouped in groups A to D. Each club played double round-robin (home and away) against fellow three group members, a total of 6 matches each. Clubs received 3pts for a win, 1pt for a tie, 0pts for a loss. The clubs were ranked according to points and tie breakers were in the following order:
 * Group Stage
 * Points earned between the clubs in question
 * Goal Differential between the clubs in question
 * Goals For between the clubs in question
 * Points earned within the group
 * Goal Differential within the group
 * Goals For within the group

The seven group winners along with the defending champion advanced to the quarter-finals.

All 8 clubs were randomly matched; however, the only restriction was that the clubs from the same country could not face each other in the quarter-finals. The games were conducted in 2 legs, home and away, and the aggregate score decided the match winner. If the aggregate score couldn't produce a winner, "away goals rule" was used. If still tied, clubs played extra time, where "away goals rule" still applied. If still tied, the game went to penalties.
 * Knockout Round

Teams
For this year the competition was restricted to clubs from countries considered 'mature' in the 'Vision Asia' paper of AFC President Mohamed Bin Hammam, with clubs from 'developing' countries entering the newly created AFC Cup and 'emerging' nations to enter the AFC President's Cup from 2005 onwards.

Mature countries
 * 🇧🇭 bahrain
 * 🇨🇳 china
 * 🇮🇩 indonesia
 * 🇮🇷 iran
 * 🇮🇶 iraq
 * 🇯🇵 japan
 * undefined
 * 🇶🇦 qatar
 * undefined
 * 🇰🇷 south korea
 * 🇹🇭 thailand
 * undefined
 * 🇺🇿 uzbekistan
 * undefined

Developing countries
 * undefined
 * 🇭🇰 hong kong
 * 🇮🇳 india
 * 🇯🇴 jordan
 * 🇱🇧 lebanon
 * 🇲🇾 malaysia
 * 🇲🇻 maldives
 * undefined
 * 🇰🇵 north korea
 * 🇴🇲 oman
 * undefined
 * 🇸🇾 syrian arab republic
 * 🇹🇲 turkmenistan
 * 🇾🇪 yemen

Emerging countries
 * 🇦🇫 afghanistan
 * undefined
 * undefined
 * undefined
 * undefined
 * 🇬🇺 guam
 * 🇰🇬 kyrgyzstan
 * 🇱🇦 lao people's democratic republic
 * 🇲🇴 macao
 * 🇲🇳 mongolia
 * undefined
 * 🇵🇰 pakistan
 * undefined
 * 🇵🇭 philippines
 * undefined
 * 🇹🇼 taiwan
 * 🇹🇯 tajikistan

Qualified Teams

 * Notes

Quarter-finals
First-leg home team shown first. First-leg home team score shown first for both legs.

Second leg
Jeonbuk Hyundai Motors won 5–1 on aggregate.

Al-Ittihad won 2–1 on aggregate.

Pakhtakor won 5–1 on aggregate.

Seongnam Ilhwa Chunma won 11–2 on aggregate.

Semifinals
First-leg home team shown first. First-leg home team score shown first for both legs.

Second leg
Al-Ittihad won 4–3 on aggregate.

Seongnam Ilhwa Chunma won 2–0 on aggregate.

Final
First-leg home team shown first. First-leg home team score shown first for both legs.

Second leg
Al-Ittihad won 6–3 on aggregate.