Since 2008, herbal mixtures with synthetic cannabinoid compounds have been sold as incense throughout the world. Although these new drugs are labeled as not for human consumption, these products are smoked for their cannabis-like effects. This study reports the structural and spectral elucidation of four cannabimimetic compounds seized in Belgium: (4-methoxyphenyl)-1-(pentyl-1H-indol-3-yl)methanone (RCS-4), 1-(5-fluoropentyl)-3-(1-naphtoyl)indole (AM-2201), 2-(2-chlorophenyl)-1-(1-pentylindol-3-yl)ethanone (JWH-203) and 4-ethylnaphthalen-1-yl-(1-pentylindol-3-yl)methanone (JWH-210). Laboratory investigations were conducted by liquid chromatography (LC)-ultraviolet spectroscopy, high-resolution accurate mass detection and nuclear magnetic resonance (NMR) analysis. This combined analytical approach allowed the detection of illicit compounds for which reference materials were not available. To facilitate identification and to complete existing databases, ultraviolet spectra and NMR data of all seized products are presented. Additionally, LC-quadrupole time-of-flight data were recorded to provide absolute identification.