During the war with Iraq in the 1980's at least 8 Chinooks were lost.
On one fateful day, 15 July 1983, an Iraqi Mirage F-1 destroyed three Iranian CH-47s flying low to deliver marines to a front line.
It's been rumored that Iranian Helicopter Company completely overhauled, re-built and reverse-engineered some models of all military helicopters including the Chinooks.
As of December 2001, the IRIAF (air force) was operating 14 CH-47Cs, including 5 completely re-built from the war. 6 others have been transferred to the Revolutionary Air Guard, "Gordane-Pasdaran" which was a separate force controlled by the air force.