Background: Regular physical therapy of people with Down syndrome improves the efficiency of such treatment. However, it remains unclear whether a discontinuation of the therapy over the period of summer holiday influences the effects of the therapeutic process. The aim of this study was to evaluate the effect of summer holiday on postural tone and quantitative parameters of body posture (angle of trunk rotation in the transverse plane and the spinal curvatures such as kyphosis or lordosis in the sagittal plane) in young people with Down syndrome.Material/Methods: Twenty one people aged 14 to 24 years were examined, with IQ scores from 54 to 35 on the Wechsler Intelligence scale. The experimental group was young people with Down syndrome whereas the control group were people with moderate intellectual disability without additional neurological, orthopaedic and other genetic disorders. The postural tone coefficient (PTC) and values of the spinal curvature (lordosis and kyphosis) and angle of trunk rotation (ATR) were evaluated twice. The first measurement was performed after 10 months of regular neurorehabilitation according to the neurodevelopment concept while the second - after 2 months of summer holiday.Results: During the holiday, the PTC value reduced significantly in the controls, from 0.40 to 0.37 (p=0.02), whereas in young people with Down syndrome, postural tone did not change significantly (p=0.33). In terms of the parameters of body posture, one significant change was observed in the group of patients with Down syndrome (kyphosis, p=0.00).Conclusions: No significant correlations were found between postural tone and values of kyphosis, lordosis and angle of trunk rotation, except for the relationship between PTC and angle of trunk rotation obtained in the main thoracic measurement (Th5- Th12, p=0.03).