Objective: To conduct an objective assessment of the level of compliance in young patients prescribed various types of removable appliances and to determine the influence of device type, treatment duration, and patient age, gender, psychological maturity, and awareness of monitoring on compliance. Materials and Methods: A total of 30 patients were fitted with either a class 2 (Frankel or bionator) or a class 3 (face mask) removable appliance, each bearing a compliance indicator chip, and they were instructed to wear them for 13 hours per day. Compliance was monitored by means of the sensor for an average of 8 months. Of the patients, 14 were informed that their appliance was fitted with a monitoring sensor, and 16 were not. The psychological maturity of all patients was assessed on the Nowicki-Strickland Locus of Control Scale, and the effect on compliance of this score as well as the patient-and treatment-related variables considered were determined via statistical analysis Results: The mean compliance recorded by the chips was 8.6 6 2.9 hours, far lower than the 13 hours prescribed, and younger patients showed significantly greater compliance than adolescents (P , .01). However, no significant differences in compliance were found between intra-and extraoral appliances, and neither gender, psychological scores, treatment duration, nor awareness of being monitored had any significant effect. Conclusions: Compliance is generally very poor in young patients, regardless of their gender and psychological maturity. Although awareness of monitoring does not appear to boost compliance, such systems may be a valuable means of providing a dentist with objective information regarding their patients' compliance. (Angle Orthod. 2017;87:88-95)