Abstract <p>The levels of potassium and sodium ions and their ratio (Na⁺/K^<i>+</i>) were assessed in the blood serum of 54 healthy donors, as well as 31 patients with Hodgkin’s lymphoma (HL) and non-Hodgkin’s lymphomas (NHL) using the capillary zone electrophoresis. Comparison of the obtained results on the content of analytes with the literature data has shown that the observed values for potassium and sodium ions in healthy donors and patients are within the normal range. However, the K^<i>+</i> content was statistically significantly higher in patients (4.4 ± 0.6 mМ) compared to the group of healthy donors (3.9 ± 0.5 mM; <i>p</i> = 0.0001), which may indicate a tendency towards impaired Na⁺/K⁺-exchanging ATPase, electrolyte balance, and metabolic processes in patients with lymphoproliferative diseases (LPD). As a result, the ratio of these cations was statistically significantly lower in patients (32 ± 5; <i>p</i> = 0.0013) compared to the control group (36 ± 4). The analysis of the homogeneity of variance between the group of healthy donors and patients showed that the variances were not homogeneous for the sodium cation (<i>p</i> = 0.0153). The average concentrations of Na^<i>+</i> and K^<i>+</i> ions did not differ significantly between the age groups of 18–50 and 51–85 years in healthy people and patients. The analysis of the homogeneity of variance between the age groups also revealed no statistically significant differences (<i>p</i> &gt; 0.05), with the exception of sodium cation in the age group of 18–50 years, where the variances were nonhomogeneous (<i>p</i> = 0.046). There were no statistically significant differences in the content of potassium, sodium ions and their ratio depending on the type of lymphoproliferative disease: HL and NHL, within the sample under study. This suggests that the content of these analytes does not depend on the type of LPD in this population.</p>