The purpose of this paper is to show how "realist synthesis" methodology (Pawson, 2002) was adapted to review a large sample of community based projects addressing alcohol and drug use problems. Our study drew on a highly varied sample of 127 projects receiving funding from a national non-government organisation in Australia between 2002 and 2008. Open and pattern coding led to the identification of 10 barrier and nine enabler mechanisms influencing project implementation across the sample. Eight case studies (four demonstrating successful implementation; four demonstrating less than successful implementation) were used for depth exploration of these mechanisms. High level theories were developed, from these findings, on implementation effectiveness in projects addressing alcohol and other drug use problems. (Contains 2 tables.)