Objective: The aim of our study was to assess the applicability of Parkinson's patients to use a dry powder inhaler correctly during their off periods, when motor function impairments like tremor, bradykinesia and rigidity are present. Background: Because of its expected rapid onset of effect, pulmonary administration of levodopa is an interesting alternative to orally administered levodopa for the rescue treatment of Parkinson's disease patients in an off period. The inspiratory flow manoeuvre performed by a patient is crucial for the performance and the suitability of a dry powder inhaler and is therefore assessed. Methods: After obtaining written informed consent, 15 patients were asked to postpone there scheduled levodopa dose in order to become off. Before the inhalation procedure started, the extent of the off state was scored by a neurologist, by using the (old) UPDRS motor section 3. Patients were asked to simulate an inhalation manoeuvre through a test inhaler (without drug), with three different resistances to air flow, in order to obtain information about their ability to inhale correctly through an inhaler during off periods. The study was approved by the ethics commitee. Results: Two patients did not become off and were therefore not included for analysis. Measurements with the other 13 Parkinson's patients during off periods showed that patients were able to perform an inhalation manoeuvre correctly, hold their breath for an acceptable time to facilitate deep lung deposition and create the pressure drop necessary to achieve a proper dispersion of a dry powder formulation, like levodopa. Conclusions: The inhalation data gathered in this study set the limits within which levodopa dry powder inhalation products for the rescue treatment of Parkinson's disease patients in an off period should effectively disperse and emit the required dose. They are, therefore, essential in any development activities towards such a product. The demonstrated ability of Parkinson's disease patients in an off period to perform an inhalation manoeuvre is expected to be sufficient for the successful development of levodopa dry powder inhalation products for the rescue treatment during an off period of this particular patient group.