While attenuated psychotic symptoms (APS) and basic symptoms (BS) are the main current predictors of psychosis in adults, studies in adolescents are scarce. Thus, we (1) described the prevalence and severity of positive, negative, disorganization, general, and basic symptoms in adolescent patients at ultra-high risk for psychosis (UHR), with other non-psychotic psychiatric disorders (PC) and with early-onset psychosis (EOP); and (2) investigated BS criteria in relation to UHR criteria. Sixty-nine 12-18-year-old adolescents (15.3 ± 1.7 years, female = 58.0 %, UHR = 22, PC = 27, EOP = 20) were assessed with the structured interview for prodromal syndromes (SIPS) and the schizophrenia proneness instrument-child and youth version (SPI-CY). Despite similar current and past 12-month global functioning, both UHR and EOP had significantly higher SIPS total and subscale scores compared to PC, with moderate-large effect sizes. Expectedly, UHR had significantly lower SIPS positive symptom scores than EOP, but similar SIPS negative, disorganized, and general symptom scores. Compared to PC, both EOP and UHR had more severe basic thought and perception disturbances, and significantly more often met cognitive disturbances criteria (EOP = 50.0 %, UHR = 40.9 %, PC = 14.8 %). Compared to UHR, both EOP and PC significantly less often met cognitive-perceptive BS criteria (EOP = 35.0 %, UHR = 68.2 %, PC = 25.9 %). BS were significantly more prevalent in both EOP and UHR than PC, and UHR were similar to EOP in symptom domains. Given the uncertain outcome of adolescents at clinical high-risk of psychosis, future research is needed to determine whether the combined assessment of early subjective disturbances with observable APS can improve the accuracy of psychosis prediction.