Objective To examine consistency between cross-sectional studies of conventional and electronic cigarette use among adolescents in terms of the measurement, analysis and reporting of parameters.

Design A systematic analysis of cross-sectional studies of conventional and electronic cigarette use in adolescents, to identify measured and reported parameters.

Data sources Studies examining use of electronic and conventional cigarette use in adolescents were identified by searching the SCOPUS database in August 2015.

Study selection The selection criteria for studies were: cross-sectional studies, in English, on e-cigarette use in adolescents. Two reviewers independently selected relevant studies from the search. 60 abstracts were identified, from which 31 papers were eligible for review (23 unique studies).

Data extraction Measured and reported parameters were identified and tabulated. These included the prevalence of cigarette and/ or electronic cigarette use, and the definitions of terms. Data were extracted independently by two reviewers.

Data synthesis With regards basic parameters of ‘ever’ or ‘current’ use of electronic or conventional cigarettes, there were 31 unique measured parameters across 23 studies. Of 16/23 studies in which authors collected information on dual current use, prevalence was reported in 11/16, with six different definitions of ‘dual use’.

Conclusions There are substantial differences in measurement and reporting of parameters across observational studies of electronic and conventional cigarette use in adolescents. These studies are at risk of reporting bias, and results are difficult to interpret. A core outcome set that should be measured and reported in all observational studies is required, using structured consensus techniques.