The present study aims to depict the importance of gender-related factors in the subjective perception of spine deformity in adolescents undergoing posterior instrumented fusion for scoliosis. Patients undergoing posterior spinal instrumentation and fusion (PSF) for idiopathic adolescent scoliosis (AIS) were recruited. The following data were recorded: gender, age, parents’ civil status, Tegner Activity Scale (TAS), body mass index (BMI), concomitant diseases, and history of neuropsychological disorders. Each patient underwent clinical and radiological evaluations according to the protocol used at our institution. All the patients were assessed before surgery using the following Patient-Reported Outcome Measures (PROMs): the Italian version of the revised Scoliosis Research Society—22 patient questionnaire (SRS-22R), the Quality-of-Life Profile for Spinal Deformities (QLPSDs) questionnaire, and the Spinal Appearance Questionnaire (SAQ). The present study recruited 80 patients (male: 19, female: 61). A significant correlation was observed between BMI, TAS, and subjective perception scores. A worse deformity perception was observed in female patients and patients with divorced parents. Gender-related factors impact the subjective perception of spine deformity in patients undergoing PSF for AIS. Specific assessment and correction are needed to improve postoperative outcomes in these patients.