Two methods, using glassy carbon paste electrode for the simultaneous determination homovanillic acid and vanillylmandelic acid, of two catecholamine neurotransmitter metabolites that can serve as biomarkers of several oncological diseases, were developed, based on differential pulse voltammetry and HPLC with amperometric detection. Low selectivity of the voltammetric method was limiting for the determination in urine samples; inclusion of chromatographic separation enabled the application in complex matrix.