This paper reports the findings of a case study that attempted to identify school-related factors influencing the quality of implementation of the Tier 1 Program of the Project P.A.T.H.S. in Hong Kong. The case study method was utilized to investigate perceptions of the program implementers of program effectiveness, and to identify the crucial factors for program success in a school with a religious background that admits students with high academic achievement. Findings demonstrated that incorporation of the program into the formal curriculum, good administrative support, efficient management from school, and presence of dedicated teachers contributed to program success. The present findings provide insight for the implementation of the Project P.A.T.H.S. in schools with a religious background. Copyright © 2011 by Walter de Gruyter Berlin Boston.