Background. Changes in the spine with achondroplasia are represented by disorders of synostosis, the presence of wedge-shaped vertebrae, underdevelopment of the sacrum, changes in the size of the roots of the arches, stenosis of the spinal canal, and changes in the sagittal balance. Aim. To investigate the clinical and radiological features of the sagittal balance of the spine in children with achondroplasia. Materials and methods. We performed a cross-sectional clinical and radiological study of 16 patients with achondroplasia aged 6–17 years (mean, 9.2 ± 3.3 years). Radiographically, the parameters of the sagittal balance of the spine and pelvis and scoliosis were evaluated. Clinical evaluation included orthopedic and neurological status and back pain syndrome. Results. The anatomic features of patients with achondroplasia are limb shortening, O-shaped curvature of the lower extremities with lateral instability of the knee joints, and flexural contractures of the hip joints. With restriction of mobility in the hip joints, compensatory mechanisms for correcting sagittal imbalance are triggered: pelvic incline, lumbar lordosis, and thoracic kyphosis change. The clinical manifestations of sagittal imbalance in enrolled children were hypokyphosis of the thoracic spine in 100% and an increase in lumbar lordosis in 56.25% of patients. In 50% of patients, wedge-shaped deformation of vertebral bodies was diagnosed at the level of the thoracolumbar transition with the formation of local kyphosis. Neurological disorders have not been diagnosed in children. Conclusions. The anatomical features of the lower limbs and hip joints in achondroplasia reflect the biomechanical features of the relationship between the spine, pelvis, and lower limbs, which should be considered when planning for orthopedic and spinal surgery after prediction.