Background and aims Addiction has been reliably associated with biased emotional reactions to risky choices. Problematic Internet use (PIU) is a relatively new concept and its classification as an addiction is debated. Implicit emotional responses were measured in individuals expressing nonproblematic and problematic Internet behaviors while they made risky/ambiguous decisions to explore whether they showed similar responses to those found in agreed-upon addictions. Methods The design of the study was cross sectional. Participants were adult Internet users (N = 72). All testing took place in the Psychophysics Laboratory at the University of Bath, UK. Participants were given the Iowa Gambling Task (IGT) which provides an index of an individual's ability to process and learn probabilities of reward and loss. Integration of emotions into current decision-making frameworks is vital for optimal performance on the IGT and thus, skin conductance responses (SCRs) to reward, punishment, and in anticipation of both were measured to assess emotional function. Results Performance on the IGT did not differ between the groups of Internet users. However, problematic Internet users expressed increased sensitivity to punishment as revealed by stronger SCRs to trials with higher punishment magnitude. Discussion and conclusions PIU seems to differ on behavioral and physiological levels with other addictions. However, our data imply that problematic Internet users were more risk-sensitive, which is a suggestion that needs to be incorporated into in any measure and, potentially, any intervention for PIU.