Aim. To determine if adenoidectomy itself could provide spontaneous relation of the transverse growth of jaws as well as an adequate mode of breathing or if there is a need for an additional orthodontic treatment to solve the problem. Methods. The study included one hundred and one patients aged 6-17 yrs., divided into three groups: group K - patients with oral respiration caused by adenoidal enlargement; group 1 - patients with adenoidectomy done 5 or more years before; group 2 - patients with orthodontic treatment done immediately after adenoidectomy. Transverse occlusion relation, the frequency of crossbite, and the intensity of nasal respiration were measured in all three groups of patients. Results. The obtained results have shown that in the patients with adenoidal enlargement and oral respiration, there was an evidence of maxillary width reduction as opposed to mandibular width. Of the patients, 14% were with unilateral or bilateral crossbite. In the patients with adenoidectomy done 5 or more years before, transverse maxillary growth compared to mandibular one in the region of the front width, showed statistically significant increase (p < 0.05) as opposed to the patients with adenoidal enlargement. The effect of adenoidectomy on transverse maxillary growth was not satisfactory anyway, which was also indicated by the increase of frequency of crossbite in 24% of the patients with adenoidectomy done 5 or more years before. In operated on and in the patients one month after orthodontic treatment, transverse maxillary growth compared to mandibular growth in all the regions of both front and back width, there was statistically highly significant increase (p < 0.01) as opposed to the patients with adenoidal enlargement and adenoidectomy done many years before. Significant maxillary and mandibular transverse relation was obtained without the presence of crossbite. Nasal respiration prevailed. Conclusion. Orthodontic therapy one month after adenoidectomy was necessary for solving the orthodontic problems caused by adenoidal enlargement and significantly contributed to the rehabilitation of nasal respiration.