Objectives: Estimate the seasonal influenza immunisation rates of family doctors / general practitioners in 2008 and establish their reasons for getting or refusing immunization. Study design: Cross-sectional study. Setting: Primary care practices in South of Portugal (Lisbon and Tagus Valley, Alentejo and Algarve regions) Participants: Family doctors / General Practitioners having regular, clinical contact with patients in the last trimester of 2008 in the aforementioned regions. Methods: A questionnaire was developed, based on published studies on attitudes and motivations of healthcare workers towards influenza vaccines, and sent by mail to a random sample of family doctors / general practitioners. Both for immunisation rates and for each appointed reason 95% confidence intervals were calculated. Results: There was a 42% response rate, although 28% were incompletely answered and excluded from analysis. Sixty two percent (CI95 55-68%) were immunized. In the immunized group, the most common reasons appointed were self-protection (100%, CI95% 96-100%), patient protection (83% CI95 75-89%), guideline compliance (83%, CI95 75-89%) and having a previous positive experience with the vaccine (71%, CI95 61-79%). In the non-immunized group, the most frequent reason was considering influenza a benign and self-limited condition (81%, CI95 49-89%). Other reasons were less often pointed out. Conclusions: Compared with previous studies, higher immunization rates were found, although the relative importance of each reason was similar. Nevertheless, in the immunized group a higher number of participants appointed guideline compliance as a reason for being vaccinated and, in the non-immunized group, the number of participants that considered influenza a benign condition was higher than in previous studies. Addressing this conviction may be a starting point for interventions aimed to increase immunization rates in this population.