The study compared motivation, psychosocial impact and perfectionism in 306 orthodontic patients (223 children and 83 adults) using the PIDAQ and FMPS questionnaires. Adults showed stronger functional motivation (p = 0.004), more interest in errors (p = 0.018), and lower parental expectations (p = 0.029). In both groups, there was a significant discrepancy between the patient's perceived aesthetic need (IOTN-AC) and the orthodontist's clinical assessment (IOTN-DHC) (p < 0.001). Higher psychosocial impact (PIDAQ) was associated with female sex, older age, higher perfectionism, and greater self-perceived aesthetic need, but not clinical need (IOTN-DHC). PIDAQ total score was the only significant predictor of higher treatment motivation (β = 0.10, p = 0.002). Adult patients experience a greater psychosocial burden and different motivational factors than children. Motivation for treatment is mainly driven by psychosocial stress, not clinical severity. Physicians should prioritize patients' perceptions and resolve disagreements for better care.