Increased pressure for evidence-based practices in policymaking and administration has led to the growth of a new research stream of implementation science. Little is known about how this new stream of research compares with scholarship on policy implementation within public administration. This paper provides a comparative review of more than 1,500 journal articles on policy and program implementation published between 2004-2013. Using bibliometric analysis and a content analysis of abstracts, implementation articles within public affairs journals and in the emerging implementation science stream are analyzed in terms of their content, methods, and focus. Following a multi-level implementation framework, this analysis considers the level at which research is taking place within the different venues of implementation research. Through this systematic review, this paper provides new insights about the current state of research, opening up new avenues for scholars to substantively engage with and contribute to this important area of study.