The number of new psychoactive substances (NPS), synthetic cannabinoids (SCs) in particular, is growing constantly. Because of the insufficiently explored effects on consumer health, they have become a major problem in the emergency departments. They are difficult to identify, and there are no antidotes that could reverse their detrimental effects. We report a case of poisoning of a young man who used SCs. The patient was admitted to the emergency department of the Clinical Hospital Merkur, Zagreb (Croatia) after sniffing and smoking a herbal product bought on the street. He presented with severe cognitive difficulties and visible eye redness. Other symptoms included somnolence, disorientation, loss of coordination, unsteady gait, hyporeflexia, stiffness, cramps and cold limbs, blurred vision, teeth grinding, dry mouth, tinnitus, fear, suicidal thoughts, impaired focus, memory, and speech, sedation, fatigue, depression, thought blocking, and autistic behaviour. His skin was dry, and his mucosa dry and irritated. Herbal products “Rainbow Special” and “Luminated Aroma” used by the patient were qualitatively analysed with gas chromatography / mass spectrometry (GC/MS) after direct extraction with an organic solvent. Solid-phase extraction method was used to analyse serum and urine samples. Despite the negative findings of biological samples, mostly due to the limitations of GC/MS, the clinical picture infallibly pointed to the poisoning with SCs. This was confirmed by the findings of 5-fluoro AMB (methyl 2-(1-(5-fluoropentyl)-1H-indazole-3-carboxamido)-3-methylbutanoate) in the herbal products.