The compliance rate of arm positioning during full-body X-rays varies depending on operative status (preoperative vs postoperative), age, and diagnosis. Retrospective cohort. Despite the importance of patients maintaining arms in the same position in preoperative and postoperative standing films, patients are known to have their arms in varying positions, confounding radiographic interpretation and making global sagittal and coronal spinal balance assessment variable and potentially less reliable. This study seeks to examine arm position compliance among adult and pediatric surgical spinal deformity patients undergoing total body X-rays over the course of 4years (2015-2018). A retrospective radiographic review was performed on 382 spinal deformity patients from July 2015 to July 2018. The study's dependent variable of interest was standardized arm position (fingers on the clavicles with shoulders in 45° of forward elevation while the patient is in a free-standing posture) observed during full-body X-rays obtained for spinal deformity evaluation. Deviations and compliance to the standard protocol for full-body X-ray arm positioning was recorded and analyzed across various independent factors, including year of surgery, pre- and postoperative periods, type of spine surgery, and patient age. Chi-square and Cochran-Armitage analyses were performed to study categorical and trends, respectively. The overall compliance rate for maintaining standardized arm position was 90% for all 370 patients (277 adult and 93 pediatric), in preoperative and postoperative setting. Adults were more likely to follow protocol than pediatric patients (92.9% vs. 82.4%, P value = 0.003). The postoperative setting observed a significantly lower overall compliance rate when compared to the preoperative period (67.8% vs. 87.0%, P value < 0.0001). Patients undergoing neuromuscular scoliosis (73.3%), vertebral column resection (VCR) (70%), and growing rod lengthening (GRL) (57.1%) had the lowest overall compliance rate in the preoperative setting. In the postoperative setting, patients with GRL, VCR, revision congenital scoliosis, congenital scoliosis, neuromuscular scoliosis, and pedicle subtraction osteotomy (PSO) surgeries were compliant less than or equal to 50% of the time. From 2015 to 2018, there was an overall statistically significant increase in compliance rate (61.1% to 90.6%). Over the study period, adult patients became significantly more compliant to protocol. This was not observed in the pediatric population. This study documented the patient compliance rate of maintaining standardized arm position during full-body X-rays of spinal deformity patients. The overall compliance rate was 90.0% for all patients in the preoperative and postoperative setting. Risk factors for lower compliance rates included patients that were pediatric, postoperative, neuromuscular, and those who underwent a complex vertebral osteotomy or GRL. There was a trend showing improved compliance rate throughout the 4-year study period, which highlights the importance of having an ancillary staff who is comfortable with a consistent standard of care protocol. These results should help other centers optimize arm positioning in their patients undergoing full-body X-rays in the future.