Abstract Introduction. Aim: to evaluate the effect of geothermal water of different mineralization on health state improvement. Material and method. A randomized controlled single blinded parallel groups interventional study was performed. 250 participants were divided into 5 groups: 3 balneotherapy (20, 40 and 60 g/l total mineralization), 1 tap water, and 1 control group. Hydrotherapy was carried out on an outpatient on everyday basis for 5 days a week over a 2-week period. The main effect on health state was measured using SHSQ-25 questionnaire after 2 weeks and each month during 3- month follow-up period. Examination by a physician and common blood and urine tests were done after the treatment period. Results and discussions. After a 2-week treatment, participants receiving all types of hydrotherapy showed a significant therapeutic response compared to the control group, especially in fatigue and mental state subcategories. The biggest total health enhancing effect after therapy was in seen in 40 g/l group, followed by 20 g/l group. The smallest effect was seen in tap water group. The most significant post-therapy effect during 3 months was given by 40 g/l procedures. Health self-rating after 2 weeks improved significantly only in geothermal water groups and lasted 2-3-month post-treatment. 2 weeks of balneotherapy had significant impact on Er, MCV, MCH, MPV, Eo, Tr, urine SG, and pH. According to the physician’s assessment, the best results after 2 weeks were in 20 g/l group, but 40 and 60 g/l water procedures gave more residual effect. Conclusions. The geothermal water of 40 g/l total mineralization has the best positive effect for health enhancement after 2 weeks and during 3-month period. 20 g/l water gives fast and short- term health effect, while 40-60 g/l water has long-lasting effect on health status.