Among the new psychoactive products, herbal mixtures containing synthetic cannabimimetics are likely the most abused worldwide. In this study, a specific ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method for the detection of 23 synthetic cannabinoids in hair samples was developed in order to (1) expand the number of screened compounds, coherent with new substances emerging in the European territory, (2) evaluate their consumption on a large period of examination, and (3) evaluate the diffusion of cannabimimetics among different populations of drug consumers. The method employs digestion of hair sample with NaOH followed by extraction with n-hexane/ethylacetate, and injection into the UHPLC-MS/MS system. After validation, the method was applied to the analysis of 344 hair samples previously tested in our laboratory for the most common drugs. Overall, 15 samples were found positive for at least one synthetic cannabinoid. Coherent with previously published results, the present data show that young males, former or still active Cannabis consumers, represent the population most often involved in synthetic cannabimimetics consumption. Several cases of poly-abuse were also determined. The drug most frequently detected was JWH-073 (11 samples) generally at low concentration (mean 7.69 ± 14.4 pg/mg, median 1.9 pg/mg, range 1.6–50.5 pg/mg), followed by JWH-122 (8 samples, mean concentration: 544 ± 968 pg/mg, median 28.4 pg/mg, range 7.4–2800 pg/mg). Other detected drugs included JWH-250, JWH-081, JWH-018, JWH-210, JWH-019, and AM-1220. For several positive samples, the synthetic cannabinoid concentration was lower than 50 pg/mg, underlining the need for established cut-off values for discrimination between chronic consumption and occasional use (or external contamination). Copyright © 2013 John Wiley & Sons, Ltd.