Background: The functional reach test in sitting position assesses dynamic balance in sitting and is used in patients with spinal cord injury. The purpose of the study was to evaluate construct and concurrent validity of the functional reach test in sitting position in patients with spinal cord injury. Methods: A convenience sample of 40 subjects was included in the study. They were assessed using the functional reach test and other tests of balance and gait. The functional reach test score was categorised according to the ASIA scale and the injury level, and correlations with clinical tests were calculated. Results: Functional reach values were the lowest in the group ASIA A and the highest in the group ASIA D. Categorisation according to the injury level revealed no meaningful categories in functional reach. Moderate correlations were established with Berg balance scale (r = 0.56), 10 meter walk test (r = 0.59) and six-minute walk test (r = 0.57). Conclusion: The functional reach test in sitting position is feasible, easy and quick to perform in patients with spinal cord injury which fulfil the inclusion criteria set. The results show good construct validity in relation to ASIA scores, and moderate concurrent validity.