A rapid HS-SPME-GC-MS (headspace solid-phase microextraction-gas chromatography-mass spectrometry) method has been developed for determination of menthone, isomenthone, neomenthol and menthol in serum samples with and without enzymatic cleavage. These flavour compounds are characteristic markers for consumption of peppermint liqueurs as well as certain digestif bitters, herbal and bitter liqueurs. This method enabled the detection of the four compounds with a limit of detection (LOD) of 2.1 ng mL^-1 (menthone and isomenthone), 2.8 ng mL^-1 (neomenthol) and 4.6 ng mL^-1 (menthol), and a limit of quantification (LOQ) of 3.1 ng mL^-1 (menthone and isomenthone), 4.2 ng mL^-1 (neomenthol) and 6.8 ng mL^-1 (menthol) in serum samples. The method shows good precision intraday (3.2-3.8%) and interday (5.8-6.9%) and a calibration curve determination coefficient (R²) of 0.990-0.996. Experiments were conducted with a volunteer, who consumed peppermint liqueur on three different days under controlled conditions. At defined intervals, blood samples were taken, and the concentration-time profiles for serum menthone, isomenthone, neomenthol and menthol, as free substances as well as glucuronides, were determined. Both menthol and neomenthol underwent a rapid phase II metabolism, but minor amounts of free substances were also detected. Menthone and isomenthone were rapidly metabolised and were found in lower concentrations and over a shorter time span than the other analytes. In blood samples taken from 100 drivers who claimed to have consumed peppermint liqueur prior to the blood sampling, menthone, isomenthone, neomenthol and menthol were detected in the serum as free substances in concentrations between 3.1 and 7.0 ng mL^-1 in eight cases (menthone), 3.1 and 11.3 ng mL^-1 in eight cases (isomenthone), 5.3 and 57.8 ng mL^-1 in nine cases (neomenthol) and 8.0 and 92.1 ng mL^-1 in nine cases (menthol). The sum values of free and conjugated substances ranged between 4.2 and 127.8 ng mL^-1 in 35 cases for neomenthol and 11.0 and 638.2 ng mL^-1 in 59 cases for menthol. Menthone and isomenthone were not conjugated. These test results confirmed that the analysis of characteristic beverage aroma compounds, such as menthone, isomenthone, neomenthol and menthol, can be used for specific verification of post-offence alcohol consumption claims.