Background: Synthetic cannabinoids (SC) are difficult to detect in urine samples, and therefore an appropriate strategy is required to investigate its potential consumption. In this work, we have designed a study to investigate SCs consumption by minors in juvenile offenders’ centres. Methods: 127 minors were selected from five juvenile offenders’ centres in the Valencian Autonomous Community (Spain). 667 urine samples were collected after their therapeutic permits with stay at home. We studied the active molecules from 7 herbal blends available at the smartshop frequented by minors. Both, the herbal blends and urine samples were analysed by liquid chromatography coupled to hybrid quadrupole time-of-flight mass spectrometry. Results: Regarding cannabis consumption, 40.2% (N=51) of the subjects reported using organic or synthetic cannabis: 5.9% of them reported only to consume synthetic cannabis, 37.2% synthetic and organic cannabis and 56.9% only organic cannabis. The urine samples analysis revealed the absence of the parent SCs investigated, but the presence of the main metabolites from two SCs (XLR-11, UR-144): N-pentanoic acid and N-(5-hydroxypentyl). The 16 individual urine samples positives to the XLR-11 metabolites could be assigned to 6 minors, 2 of which recognize consumption whereas the remaining 4 adolescents did not recognize consumption of SCs. Conclusions: Synthetic cannabinoids, specifically, XLR-11, are consumed in juvenile offenders’ centres in the Autonomous Valencian Community. Preventive and therapeutic interventions in minors housed in those centres must be implemented to reduce the consumption of new psychoactive substances and to improve the risk-perception of these substances.