The purpose was to analyze preoperative symptoms, curve characteristics, and outcome of surgery in patients operated on for isthmic spondylolisthesis with concomitant scoliosis. Overall, 151(9.1%) of 1667 scoliosis patients had spondylolisthesis treated surgically in 21 (13.9%)(19 females, 2 males; 11 low-, 10 high-grade). Patients' age at admission was 13.5(10-17)y. Preoperatively, 5/21 were pain-free (1 high-grade, 4 low-grade), 7 (2 high-grade) had LBP, 2 (both high-grade) radiating pain, and 7 (5 high-grade) had both. Hamstring tightness was present in 5/10 high-grades. Scoliosis was primary thoracic in 3/11 low-grade and secondary lumbar with oblique rotated take-off of L5 in 8/11 low-grade patients. Of the high-grades, 7/10 had sciatic curves and 3 secondary lumbar. In low-grades, the main indication for surgery was pain in 3/11 and lumbar curve progression or the intent to prevent it in 7/11. The operative technique was uninstrumented posterolateral fusion in 8/11, instrumented L4-S1 fusion with reduction of L4-tilt in 2, and direct repair in 1 patient. High-grades were fused to prevent further slipping regardless of subjective symptoms (uninstrumented anterior 5, combined 2, instrumented reduction 3). Selective thoracic fusion for scoliosis was performed in 3 patients. None of the lumbar curves needed fusion. All sciatic curves resolved. The follow-up time was 10.6(2-21)y. Of the low-grade patients, 5 were pain-free, 4 had moderate pain, and 2 had a severe chronic pain syndrome. One had broken pedicle screws without sequelae. Of the high-grade patients, 4 were pain-free, 6 had moderate pain. One had a pain-free peroneal weakness after slip reduction.