Introduction. Due to the unprecedented development of media and information technology, modern lifestyles have been changing from active to passive (sedentary). A sitting position dominates today both in the professional and the non-professional sphere of people’s life. It seems that a human does not realize what is the position of individual segments of his body, especially the torso while sitting. The torso, as the segment with the highest mass, is the source of the highest mechanical loads acting on the spine. Hence, in the habitual sitting posture, the optimal spine position has been lost. Objective. The aim of this study is to analyze statodynamic parameters of the spine in a sitting position and answer the question which of them determine the habitual sitting posture. Material and methods. The study included 372 people declaring themselves as healthy. The research program consisted of statodynamic parameters of the spine in a standing position and in 6 sitting positions: sitting position freely, favourite sitting position, sitting position with a crossed leg over the right and left thigh, and sitting position with a feet resting on the left or right knee. Results. The conducted research has shown that setting the spine in a habitual sitting posture is determined only by a change in the statodynamic parameters in the sagittal plane and generally does not depend on the range of motion in other planes. Conclusions. Habitual sitting postures are determined by the size of angles of the thoracocervical and thoracolumbar transitions as well as the size of the amplitude of the pelvic movements. The research has indicated worrying trends to misuse of kinematic redundancy in the spine while sitting in the sagittal plane.