Background:
Although moving from smoking to electronic nicotine delivery systems (ENDS) could reduce the harms smokers face, many ENDS users continue to smoke tobacco. We explored the contributing factors to tobacco use among ENDS users.

Methods:
We conducted in-depth interviews with n=20 past 30-day ENDS and tobacco users (16 used ENDS daily; the median duration of ENDS use was 4.5 months). Interviews explored motivations for using ENDS, experiences of using ENDS and tobacco, and dual use patterns. We used qualitative thematic analysis to analyse interview data.

Results:
Most, but not all, participants used ENDS to try and quit smoking entirely. Among those who reported trying to quit, social exposure to tobacco use and alcohol consumption cued cravings and undermined a full transition to vaping. Some participants found ENDS did not sufficiently alleviate stress or replicate the nicotine hit, mouth-feel or rituals they experienced with smoking. The convenience and perceived social acceptability of using ENDS indoors also facilitated dual use. Several participants cited financial reasons as the primary motivation for using ENDS; they reported alternating between ENDS and smoking as rationing their 'real' cigarettes helped manage the cost of tobacco. Younger, social tobacco smokers reported experiencing stigma when using ENDS, which inhibited their ENDS use in some social settings where tobacco use was normative. While many participants saw dual use as a transition towards becoming smokefree, others viewed their reduced smoking levels alongside ENDS use as a successful outcome. Some perceived ENDS as healthful, not merely less harmful than tobacco; this view appeared to offset dissonance about using tobacco and positioned cigarette smoking as a reward for being "good".

Conclusions:
Understanding factors that facilitate and support dual use of ENDS and smoked tobacco may help inform interventions that support ENDS users to make a full transition from tobacco smoking to vaping.