Set of the lab-made boron-doped diamond electrodes (BDDEs) prepared with various B/C ratio (1000, 2000, 4000, 8000, 10,000, and 20,000 ppm) in the gas phase was subjected to the detailed characterization in the present paper. It was proved, that the B/C ratio influenced the electrochemical features of the working electrodes like a width of the potential window, which decreased with increasing B/C. Variations of reversibility of two redox systems (Fe(CN)(6)(3-/4-) and Ru(NH3)(6)(2+/3+)) depending on B/C were observed as well. The best electrochemical properties were found for BDDE with B/C 10000 ppm. Moreover, the working electrodes were tested for voltammetric analysis of leucovorin based on its oxidation. The lab-made BDDEs were applied for voltammetric analysis of the pharmaceutical preparation containing leucovorin with excellent results (recovery 97.7-103.3%, RSD5 <= 2.1%).