Lipophilic amines are recognized as important tracers for brain imaging. Their pulmonary accumulation was a drawback for optimal concentration in the brain. We used IMP, HIPDM, IP, amphetamine derivatives to determine the relation between structure and accumulation in the lung. The incubation of phenylalkylamines in competition with 3H-Imipramine, for human lung membrane and microsomes was performed and led to the extraction of a competitive constant (KI). The results showed that the compounds can be classified in order of their decreasing affinity: Iodoamphetamine, iodoisopropylamphetamine, dimethyliodophentermine, hydroxyiodobenzyl propane diamine (HIPDM), isopropylamphetamine and amphetamine. Iodine set in the para position of the ring seemed to increase the affinity of phenylalkylamines for the lung. Adjunction of isopropyl or methyl groups to the lateral chain decreased this affinity.