ObjectivesTo investigate the role of socioeconomic status and psychological stress to potential associations between confidence in the future and a wide range of health-related behaviours.DesignWeb-based cross-sectional study including an ‘Electronic Health Check’ at the Finnish Happiness-Flourishing Study website linked to a TV programme on happiness and depression.SettingThe Finnish population with access to the internet.Participants101 257 Finns aged 18 and above (21 365 men; 79 892 women). Participants who were under the age of 18 and who did not provide information about their gender were excluded.Primary outcome measuresAs planned, we assessed smoking, weekly alcohol consumption and binge drinking, daily intake of fruits and vegetables and regular exercise.ResultsCompared with participants with low confidence in the future, those with high confidence were less likely to be daily smokers (men OR 0.58, 95% CI 0.52 to 0.65; women 0.57, 95% CI 0.53 to 0.61) and binge drinkers (men 0.57; 0.52 to 0.63; women 0.54; 0.50 to 0.57). Participants with high confidence in the future were more likely to exercise regularly (men OR 2.82, 95% CI 2.55 to 3.13; women 2.57, 95% CI 2.44 to 2.71) and consume vegetables (men OR 2.48, 95% CI 2.25 to 2.74; women 2.13, 95% CI 2.03 to 2.24) and fruits (men OR 2.09, 95% CI 1.86 to 2.35; women 1.83, 95% CI 1.74 to 1.93) daily. Adjustment for current psychological distress and satisfaction for income attenuated the results.ConclusionsHaving confidence in the future is strongly associated with a healthy lifestyle, as assessed by a healthy diet, physical exercise and substance abuse. Health-related interventions may benefit from tailoring interventions according to the target population's level of confidence in the future as well as their level of psychological distress.