OBJECTIVES: In view of the 2009 emergence of Influenza A (H1N1) and the declaration of a phase 6 pandemic by WHO, Greece established a voluntary vaccination program for the entire country population. The aim of the present study was to investigate factors affecting individuals’ decision to participate. METHODS: We conducted repeated weekly telephone surveys until a random sample of 12,639 households stratified according to place of residence (geographical area and level of urbanization) was formulated. The interviews were based on a strictly structured questionnaire designed for the purpose of the study. A logistic regression analysis was conducted in order to identify the factors that influence individuals’ decision to be vaccinated against H1N1. The Hosmer–Lemeshow criterion was used to check the model’s goodness of fit. RESULTS: Higher levels of personal education (Odds Ratio: 0.61) and income (OR: 0.42) were associated with a negative decision to participate to the vaccination program. However, when an interaction term between the two variables was used, individuals of both higher education and income were more likely to have participated in the program (OR: 1.26). On the contrary, increased levels of concern/fear for the H1N1 and increased confidence to the personal/family physician, both measured in a 5-point Likert scale, showed a positive relationship. The Hosmer–Lemeshow goodness of fit test statistic was 0.98 suggesting satisfactory fit of the model. CONCLUSIONS: In Greece, a country where less than 5% of the total population participated to the voluntary vaccination program against H1N1, socioeconomic status, as expressed through income and education, the role of the family physician and the personal attitude towards H1N1 were important factors for a positive decision. In the case of similar future efforts, these variables should be taken into account, in order to facilitate focused interventions.