This study evaluates brain perfusion in long-term inhalant abusers of toluene, acetone, benzene and derivatives. Ten patients in the age range 16-18 years (mean, 17.3+/-0.67 years), who had been inhalant dependent for a mean period of 48.3+/-6.2 months, but who had stopped using inhalants for 1-11 months (mean, 5.4+/-2.1 months), and ten controls (mean age, 17.3+/-0.67 years) were included in the ... [Show full abstract] study. Psychiatric tests, biochemical tests and Tc-99m-hexamethylpropyleneamine oxime (Tc-99m-HMPAO) brain single photon emission computed tomography (SPECT) were performed on all patients. Brain SPECT images were evaluated qualitatively and quantitatively. The mean IQ level was found to be 84 (by psychological tests). Brain SPECT showed non-homogeneous Tc-99m-HMPAO uptake and hypoperfusion areas in all patients (five left temporal, one right temporal, two left temporal plus bilateral parietooccipital, one biparietal and one left temporoparietal). Seven patients had hyperperfused foci (unifocal in five patients and multifocal in two patients). Six hyperperfused foci were in a parietal and one in a temporoparietal location. This study suggests that inhalant dependents exhibit serious abnormalities in brain SPECT images, including hypo-hyperperfusion foci and non-homogeneous uptake of the radiopharmaceutical. A further study with a larger number of patients and long-term follow-up may help to reach a more specific conclusion.