Introduction Addictions are associated with decision making impairments. The present study explores decision making in Substance use disorder (SUD), Gambling disorder (GD) and Obesity (OB) when assessed by Iowa Gambling Task (IGT) and compares them with healthy con- trols (HC). Methods For the aims of this study, 591 participants (194 HC, 178 GD, 113 OB, 106 SUD) were assessed according to DSM criteria, completed a sociodemographi c interview and con- ducted the IGT. Results SUD, GD and OB present impaired decision making when compared to the HC in the over- all task and task learning, however no differences are found for the overall performanc e inthe IGT among the clinical groups. Results also reveal some specific learning across the task patterns within the clinical groups: OB maintains negative scores until the third set where learning starts but with a less extend to HC, SUD presents an early learning followed by a progressive although slow improvement and GD presents more random choices with no learning. Conclusions Decision making impairments are present in the studied clinical samples and they display individual differences in the task learning. Results can help understanding the underlying mechanisms of OB and addiction behaviors as well as improve current clinical treatment s. ; This manuscript was supported by grants from Instituto Salud Carlos III (ISCIII; FIS PI14/ 00290 and CIBERobn) and co-funded by Fondos Europeos de Desarrollo Regional (FEDER) funds - a way to build Europe, and AGAUR (2014 SGR 1672). This manuscript was co-funded by Ministerio de Economía y Competitividad (PSI2015-68701-R). CIBERobn and CIBERSAM are both initiativesof ISCIII. José C. Fernández-García is recipient of a research contract from Servicio Andaluz de Salud (SAS) (B-0033-2014).