In this research, we reviewed indirect comparison methodology in the context of HTA (Health Technology Assessment) when head-to-head trials are absent or lacking. As an example of HTA using indirect comparison, the study <Efficacy of Atomoxetine and Methylphenidate in Attention Deficits Hyperactivity Disorder in Adults: A Rapid Review> conducted by NECA in 2012 was selected as an exemplar. This study was a short-term rapid review and meta analysis of each treatment was not possible for given time frame.