The aim of this study was to compare treatment provided to adult heavy and low users of dental services in the Finnish Public Dental Service (PDS) and to analyse changes in patients' oral health status. We assigned all adults who attended the PDS in Espoo in 2004 to a group of heavy users (n = 3,173) if they had made six or more dental visits and to a comparison group of low users (n = 22,820), if they had made three or fewer dental visits. Data were obtained from the patient register of the PDS. A sample of 320 patients was randomly selected from each group. Baseline information (year 2004) on age, sex, number and types of visits, oral health status and treatment provided was collected from treatment records. Both groups were followed-up for five years. Restorative treatment measures dominated the heavy and low users'treatments; 88.8% of heavy users and 79.6% low users had received restorations during the five-year period. Fixed prosthetic treatments were provided to just 2% of the heavy users and 0.8% of the low users. Emergency visits were more common for heavy users (74.8%) than for low users (21.6%) (p