Synthetic cathinones are one of the major pharmacological families of new psychoactive substances (NPS). We report a case of a young man who was found dead a couple of hours after sniffing substances bought on the Internet from Spain. 3-methylmethcathinone (3-MMC) was identified during general unknown screening by liquid chromatography with diode array detector and gas chromatography coupled to mass spectrometry. Quantification of 3-MMC was performed by gas chromatography tandem mass spectrometry after solid-phase extraction. Toxicological analysis of postmortem peripheral blood, cardiac blood, vitreous humor, bile and urine revealed 3-MMC in concentrations of 249ng/mL, 609ng/mL, 2988ng/mL, 1291ng/mL and 29,694ng/mL, respectively. Powder and crystals seized at victim's home contained 32.9% and 36.9% of 3-MMC, respectively. No other xenobiotics were detected in postmortem samples. The cause of death was 3-MMC intoxication and the manner was accidental.