This study investigated the orthodontic treatment of 429 consecutive patients [172 male (40.1 per cent) and 257 female (59.9 per cent)] carried out by 10 orthodontic specialist practitioners in seven European countries [two in the Czech Republic (A and B), two in Germany (A and B), Italy, Latvia, Lithuania, and Netherlands, and two in Slovenia (A and B)]. The median age of the patients at the start of treatment was 13.0 years (minimum 7.3 years maximum 50.3 years). The patients had a range of malocclusions and the majority (97 per cent) were treated with upper and lower fixed appliances. Real exchange rates were calculated using purchasing power parity (PPP) indicators to allow cross-border comparisons of costs. The Index of Complexity, Outcome and Need (ICON) was used to measure the effectiveness of treatment and cost per ICON point reduction to compare cost-effectiveness of orthodontic treatment between practitioners in different European countries. The median cost per ICON point reduction for all the cases treated was 57.69 euro. The median cost per ICON point reduction varied greatly between practitioners from 21.70 euro (Lithuania) to 116.62 euro (Slovenia A). Analysis of variance and Tukey post hoc tests showed the differences in cost-effectiveness between the practitioners to be statistically significant (P<0.001). The cost per ICON point reduction is a simple and effective method of comparing cost-effectiveness between orthodontic practitioners in different countries.