The objectives of the study were to compare the costs and outcome of orthodontic treatment in eight municipal health centres in Finland. A random sample of the age groups of 16- and 18-year-olds (n = 1109) living in these municipalities was clinically examined by two calibrated orthodontists. The acceptability of the morphology and function of the occlusion were assessed with the Occlusal Morphology and Function Index (OMFI). The data concerning previous orthodontic treatment were collected from the patient records of all subjects (n = 608) who reported previous or ongoing orthodontic treatment or who could not recall if they had received orthodontic treatment. The health centres were grouped into an early and a late timing group according to the mean age of starting the treatment. The mean age for starting orthodontic treatment was 8.0 years (SD 1.9) in the early group and 10.7 years (SD 2.3) in the late group. The visit costs and the costs of orthodontic appliances without overheads comprised the operating costs. The cost-effectiveness of orthodontic services was measured by estimating how much each health centre had to have paid for one per cent unit of acceptable morphology and acceptable function of occlusion. The mean appliance costs were higher in the late timing group and the mean visit costs higher in the early timing group. The mean operating costs per case were €720 in the early and €649 in the late timing group. However, there was a great variation within both groups. The cost of one per cent unit of acceptable morphology was the same in the two timing groups, while the cost of one per cent unit of acceptable function was lower in the early timing group. The low operating costs as such did not totally explain the better cost-effectiveness of orthodontic care. Furthermore, the cost-effectiveness was not directly connected with the timing of treatment.