Idebenone is a quinone analog that is applied in the treatment of several neurological disorders including Friedreich ataxia and mitochondrial encephalomyopathies. Our aim was to develop an easy and sensitive analytical HPLC-procedure for the determination of idebenone in the serum of patients treated with this drug. Serum samples from nine paediatric patients diagnosed with Friedreich ataxia and receiving idebenone treatment were analyzed. Idebenone was separated from serum by reverse high-pressure liquid chromatography and analyzed using an electrochemical detection procedure. No interferences were observed during analysis of patient samples obtained prior to idebenone treatment. Calibration of idebenone concentration indicated a linear range between 500 pmol/l and 5 micromol/l and calculation of within-run and between-run coefficients of variation suggested adequate analytical quality for reliable determination. In agreement with previously reported data, during drug therapy, idebenone serum concentrations (basal conditions, range 0.1-0.49 micromol/l) were greatly elevated 90 min after an oral dose (range 0.66-3.63 micromol/l). Thus, we have developed a simple and rapid method that offers adequate analytical quality for accurate idebenone determination.