ABSTRACT Alcohol consumption and Internet use are highly prevalent behaviours among young adults and previous research has suggested that different addictive behaviours might be distinctly associated with personality. This study examined the role of big-5 personality traits in alcohol consumption and Internet use. Alcohol consumption, internet use, and personality traits were assessed on 457 Portuguese university students. Higher levels of neuroticism, and lower levels of conscientiousness and agreeableness were found to be associated both with harmful alcohol use and problematic internet use. Openness to experience was not correlated with either behaviour. Multiple linear regression showed that conscientiousness might be an important predictor of both alcohol consumption and Internet use. There is an important overlap in personality traits related to alcohol and the use of internet, but there are also clear differences in what regards extraversion. Conscientiousness should be promoted as a preventive strategy.