Objectives: To assess perceived needs for dental treatment (PNDT), oral health-related quality of life (OHRQoL) and oral diseases in a Thai schoolaged national representative sample. In addition, relationships between PNDT and various aspects of OHRQoL, different levels of oral diseases as well as sociodemographic characteristics were assessed. Methods: Study sample was a subsample of Sixth Thailand National Oral Health Survey. Data were collected on 1063 12-year-olds and 811 15-year-olds through oral examinations, interviews on PNDT and OHRQoL, using Child-Oral Impacts on Daily Performances (Child-OIDP) or Oral Impacts on Daily Performances (OIDP) indices and questionnaires containing questions on sociodemographic information. Results: Prevalence rates of PNDT were 60.4% in 12-year-olds and 67.6% in 15-year-olds. PNDT were highly associated with OHRQoL with significant odds ratios that increased incrementally by the intensity of oral impacts. Oral impacts on eating, emotional stability and smiling and those attributed specifically to dental caries, periodontal diseases, malocclusion and tooth discolouration were associated with PNDT. The chances of having PNDT increased by number of untreated decayed teeth. Periodontal disease was associated with PNDT only when occurring to a great extent. Boys and children in some regional rural areas were less likely than girls and those living in Bangkok to have PNDT. Conclusions: Perceived needs for dental treatment were common and highly associated with levels of oral impacts, specifically impacts on eating, emotional stability and smiling performances. PNDT were also related to number of untreated decayed teeth, a great extent of periodontal disease, sex and geographical region.