Introduction: The Spinal muscular atrophy (SMA) is the most common disease of the lower motor neuron, which appears in the 1/6-10,000 births. It manifests as muscle atrophy and weakness. SMA is an autosomal recessive disease that is most commonly caused by a deletion of 7th and 8th exons of the gene Survival Motor Neuron 1 (SMN1). There are five subtypes of the SMN1 related SMA: type 0 develops before birth, types 1, 2, and 3 from a young age and the type 4 in adulthood. Purpose: The purpose of this diploma work was to assess whether the motor function in adult SMA patients, measured by the Hammersmith functional motor scale expanded (HFMSE) is associated with the muscular strength of the hand grip, the key grip and the 6-minute walk test. Methods: The study sample was comprised of 31 adult patients with a genetically confirmed diagnosis of SMA, who are followed in the Institute of clinical neurophysiology, UKC Ljubljana. They were tested with the HFMSE, hand held dynamometry test and the 6-minute walk test. For the statistical analysis of the data, we used Spearman correlation test. Results: There is statistically significant correlation between higher score on the HFMSE and the greater hand grip strength in the right and the left hand (right hand r = 0,85, p < 0,0001; left hand r = 0,82, p < 0,0001). Furthermore, there is also statistically significant correlation between higher score on the HFMSE and the greater key grip strength in the right-hand and left hand (right hand r = 0,78, p < 0,0001; left hand r = 0,89, p < 0,0001). There is also a positive correlation between the HFMSE, and the 6-minute walk test (r = 0,80; p < 0,0001). Discussion and conclusion: Results of our study show that motor function of adult SMA patients, measured by the HFMSE correlates with the muscular strength of the hand grip, the key grip between the thumb and the index finger, and the 6-minute walk test. The obtained results will be helpful to the researchers who will be monitoring the patients and the progression of the disease or the effectiveness of drugs, while being indicators of the current motor state of the patient. For future research, we suggest using more precise (digital) dynamometers tests and the separation of the SMA patients, based on the SMA type.