The report by Europe's leading human rights watchdog says Bosnia, Britain, Cyprus, Germany, Greece, Ireland, Italy, Macedonia, Poland, Portugal, Romania, Spain, Sweden, and Turkey either actively or passively colluded in the practice.
Some are accused of bearing "responsibility in varying degrees" for rights violations.
The report states that it is clear authorities in some European countries "actively participated" with the CIA in unlawful activities. It says other governments "ignored those practices knowingly, or did not want to know."
Poland and Romania were singled out for tolerating the operation of CIA secret detention centers.
Polish Prime Minister Kazimierz Marcinkiewicz has called the report "slanderous" and said it is "not based on any facts."
Norica Nicolai, the head of a Romanian parliamentary commission investigating alleged CIA flights to Romania, rejected the report's accusations that Romania harbored CIA detention centers as "pure speculation."
Government officials, some of them unnamed, from Britain, Macedonia, and Spain have also criticized the report for allegedly not proving its allegations.