Aim. To evaluate the orthodontic treatment effects, performed immediately after adenoidectomy, on lips relation, overjet and class (Angle). Methods. Three groups of patients, aged 6−17 years, were observed: group K - patients with oral respiration caused by adenoidal enlargement; group 1 - patients with adenoidectomy performed five and more years previously; group 2 - patients with one year of orthodontic treatment performed immediately after adenoidectomy. Lips and overjet status and class (Angle) was measured in the examined patients. Results. In all of the three examined groups, there was a statistically highly significant increase (p<0.01) of competent lips. In the patients of group K, the overjet values ranged from 1 mm up to 12 mm where 90% of them had overjet > 4 mm and 6% < 1 mm. The front open bite, low overbite and reversed overjet was found in the patients with low overjet in this group, as well. Overjet values in the patients of group 1 ranged from -2 mm up to 12 mm where 86% had overjet > 4 mm and 10% < 1 mm. Significantly higher increase (p<0.01) of overjet values (1−4 mm in 94% of patients) was observed in the patients of group 2 in comparison to the values found in the patients from groups 0 and 1. Class II (Angle) was recorded in 81% of the patients in group 0, and 79% in group 1, while class I (Angle) was observed 100% only in the patients of group 2. Conclusion. Orthodontic treatment immediately after adenoidectomy was necessary for achieving the competition lips relation, normal overjet and class I (Angle).