This project is focused on studying e-cigarette Product Characteristics and Frequency of Smoking Among Young Adults. Previous research suggests that e-cigarette use is associated with cigarette initiation, including the frequency and heaviness of cigarette smoking. The goal of this research is to examine the impact of specific e-cigarette characteristics on cigarette smoking frequency. What we did is to use advanced counts model to model the association between the e-cigarette exposures and the outcome, the number of cigarette use in the past 30 days.