Objective: To assess blood pressure (BP) change in relation to hydration status measured clinically and by bioimpedance spectroscopy method (BIS) in chronic hemodialysed patients. Design and method: A 10 months, one centre retrospective analysis was performed on the group of 48 regularly hemodialysed patients (M/W: 15/33) to analyse the BP change in relationship to hydration status measured clinically (weight, dry weight, intradialytic weight gain,) and by BIS: overhydration (OH), extracellular water volume (ECW), total body water volume (TBW) and rates OH/ECW and ECW/TBW before and after the hemodialysis. Patients were divided into different regions based on their BP levels before hemodialysis and hydration status, which was measured by BIS. The relationship between BP and hydration status change was also evaluated. Results: The significant change of systolic BP (p < 0,001; 95%CI 3,7–7,0 - p < 0,004, 95%CI 0,49–3,8) and diastolic BP (p < 0,001; 95%CI 1,0–7,0 - p < 0,0038; 95%CI 0,49–3,8) was identified in the first 3 hours of the hemodialysis, and also in relation to the weight loss measured clinically (p < 0,001; r = 0,17) and to the hydration status assessed by BIS (p < 0,001; r = 0,19). The rate OH/ECW revealed a significant correlation to systolic BP (p < 0,02; r = 0,10) and ECW/TBW to diastolic BP (p < 0,006; r = 0,12) before hemodialysis in comparison to the clinically measured hydration. 6% of patients were found to have both normal level of BP (<140 mmHg) and overhydration (−1-+1l). In 32% of analysed group reached range of BP < 150 mmHg and overhyhydration <2,5l. Volume dependent hypertension (BP >150 mmHg; HS >2,5l) was documented in 27%. The region of severe heart impairment represented 33% of our group (BP <140 mmHg, overhydration >2,5l). 2% represented the population with BP >150 mmHg and mild overhydration 1,1–2,5l. Conclusions: It was identified that the amount of overhydration played an important role in one third of the analysed patient group. In addition, a decrease of blood pressure was observed in relation to the fluid removal. BIS hydration parameters seem to be more suitable predictors of blood pressure level before hemodialysis compared to the clinically measured hydration status.