OBJECTIVES: Parkinsonian syndromes (PS) can be difficult to diagnose clinically, the most common condition misdiagnosed as PS being essential tremor (ET). DaTSCAN (123I-FP-CIT) SPECT imaging accurately differentiates PS with dopaminergic deficit from ET in patients with uncertain clinical diagnosis (sensitivity 95%, specificity 93%). This study aimed to assess the economic value of using DaTSCAN to the Belgian Health care system. METHODS: A Markov model was developed to simulate a cohort of patients with clinically uncertain PS managed over 5 years 1) without DaTSCAN (treatment based on clinical judgement), or 2) all patients receiving DaTSCAN at the outset. Health states were defined by type of therapy (PS first-line, PS second-line, ET, none) and underlying condition (PS, ET). The model estimated time on appropriate therapy (PS therapy for underlying PS, ET therapy for underlying ET) and patient management costs. Model inputs were from published studies, with treatment patterns/resource use from a Delphi panel of 13 Belgian physicians. 53% cohort members were assumed to have true PS. Costs were from official sources, the test cost (agent plus administration) being €900. RESULTS: Without DaTSCAN, 41% of cohort members were treated appropriately at the outset, rising to 75% at 5 years. Using DaTSCAN, 94% of patients were treated appropriately at the outset, declining to 77% at 5 years. DaTSCAN use generated an incremental 1.40 'adequately treated years' at a net cost of €140 per patient. This result was sensitive to the underlying prevalence of PS, but relatively robust to variations in other model parameters, such as rates of adverse events and withdrawal from therapy. CONCLUSION: Treatment of patients with clinically uncertain PS based on DatSCAN rather than clinical judgement may be considered to be an economically favourable strategy. An increase in time on appropriate therapy is achieved at modest extra cost to the Health care system.