Several authors have determined clinically the width of attached gingiva (AG) over the deciduous and early permanent dentitions in children. They have noticed that when comparing the width of AG over deciduous teeth to the width of AG over the succeeding newly erupted permanent teeth, a clear diminishing in AG can be seen. The aim of the present cross-sectional study was to assess the width of radiologically-defined AG (RAG) over the permanent teeth of 6-, 10- and 12-year-old children. Altogether 123 subjects were recruited. The mucogingival junction (MGJ) was revealed with Schiller's iodine solution and marked over each tooth with a piece of metal wire before taking a panoramic radiograph. The width of RAG over permanent teeth was measured from the radiographs as the midfacial distance from the cementoenamel junction to the mucogingival junction. When comparing the width of RAG over 1st molars and the 1st and 2nd incisors, statistically significant differences were found between 6- and 10-year-olds, between 6- and 12-year-olds and between 10- and 12-year-olds. For the 1st maxillary incisor, the difference in width was not statistically significant between ages 10 and 12 years. The findings seem to justify the conclusion that an inadequate width of AG will correct itself from 6 to 12 years of age without interference by means of periodontal surgery.