Have you ever wondered why the randomized controlled studies on electronic cigarette use often produce different results from the findings of observational studies? A leading e-cigarette researcher advanced some reasons that could explain those discrepancies. This was during a presentation made at the 2017 Electronic Cigarette Summit in the UK. For example, he suggests that controlled trials often show a lesser impact of e-cigs as quit smoking devices because those who have already succeeded in using e-cigs to quit are eliminated as study subjects. This leaves those who are struggling to use the method or those just starting out on their quest to quit smoking as study subjects. Observational studies capture those who have succeeded already in their findings. Similarly, RCTs often have different baseline vaping standards/definitions from the baselines defined by observational studies. It is therefore possible that RCTs underreport the value of switching to vaping when compared to observational studies. This presentation will help you to make sense out of the results of the two kinds of findings that may initially appear contradictory.