The main purpose of the present work was studying the biodistribution of amikacin solid lipid nanoparticles (SLNs) after pulmonary delivery to increase its concentration in the lungs for treatment of cystic fibrosis lung infections and also providing a new method for clinical application of amikacin. To achieve this aim, (99m)Tc labelled amikacin was loaded in cholesterol SLNs and after in vitro optimization, the desired SLNs and free drug were administered through pulmonary and i.v. routes to male rats and qualitative and biodistribution studies were done. Results showed that pulmonary delivery of SLNs of amikacin by microsprayer caused higher drug concentration in lungs than kidneys while i.v. administration of free drug caused reverse conditions. It seems that pulmonary delivery of SLNs may improve patients' compliance due to reduction of drug side effects in kidneys and elongation of drug dosing intervals due to the sustained drug release from SLNs.