The prevalence of tobacco smoking amongst people with bipolar disorder in the USA has been estimated at 66%. The impact of tobacco smoking on physical health and financial burden has received considerable attention, however the impact of tobacco smoking on mental health is less well understood. Two studies have found an association between tobacco smoking and adverse outcomes in bipolar disorder. A 24-month, naturalistic, longitudinal study of people with bipolar disorder (N=175) or schizoaffective disorder, bipolar type (N=64) found that daily smokers had poorer scores on the CGI-Depression (p=0.034) and CGI-Overall Bipolar (p=0.026) scales, and had lengthier stays in hospital (p=0.012), compared to non-smokers. A study investigating post hoc the results of drug trials for the treatment of mania analysed participants according to smoker status. Non-smokers showed superior treatment outcomes on both the YMRS (P=0.002) and CGI-BP (P<0.001) scales, and longer time to discontinuation for any cause utilising Kaplan–Meier survival curves. These studies suggest that encouraging cessation of smoking amongst patients with bipolar disorder as well as implementing smoke free policies in medical settings may have mental health benefits as well as improve physical health and well-being.