The aim of this study was to analyze the relationship between treatment adherence and subjective well-being (positive and negative affects and satisfaction with life) in HIV/AIDS infection. The empirical study was conducted at two Portuguese hospitals (Porto and Lisbon) with a sample of 197 outpatients diagnosed with HIV/AIDS attending the Infectology service and on antiretroviral medication, during a 6-month period (February-July 2009). All patients were asked for voluntary fulfillment of the questionnaire which recorded information on different socio-demographic variables. Clinical records were inspected in order to collect additional clinical information from the patients. The "Questionnaire to Assess Adherence to Antiretroviral Treatment-HIV" was used in order to assess the adherence degree in Portuguese version of Reis et al. The Portuguese versions of "Positive and Negative Affect Schedule" (PANAS) and the "Satisfaction with Life Scale" were used to measure subjective well-being. The study collected evidence on the positive correlation between therapeutic adherence (assessed by CEAT-VIH) and positive affect, as well as between adherence and satisfaction with life. Differences in therapeutic adherence and positive affect according to some clinical variables were also found. The multiplicity and the interaction of several determinants are being considered in the adjustment process during treatment for HIV/AIDS. The results may have implications for the psychological intervention directed at improving adherence to antiretroviral therapy.