A voluntary professional quality improvement project involving preventive departments and vaccination centres of an Italian region was carried out through two surveys (in 2001 and in 2006) performed using a quality assessment manual including 12 standards and 157 criteria. After the first survey, a feedback was sent to all participating centres. All six local health authorities participated, as well as all regional vaccination centres, 48 in 2001 and 41 in 2006. The overall adherence rate to the criteria was 56.0% (3258/5820) in 2001 and 74.4% (3784/5085) in 2006. The improvement was obtained without mandatory interventions from regional authorities.