Posaconazole is superior to fluconazole (FLU) and itraconazole (ITRA) in the prevention of invasive fungal diseases (IFDs) in neutropenic patients with acute myelogenous leukemia (AML) and myelodysplastic syndrome (MDS). A new tablet formulation of posaconazole with improved pharmacokinetic and pharmacodynamic properties compared to posaconazole oral solution has recently been approved. The objective of this study is to estimate the cost-effectiveness of the newly developed posaconazole tablets versus FLU oral suspension or ITRA oral solution for preventing IFDs in high-risk neutropenic patients with AML or MDS and from the perspective of the Spanish National Health System (NHS). A previously validated economic model was used. The probabilities of experiencing an IFD, an IFD-related death or death from other causes over 100 days were based on clinical trial data and input into a decision tree. Surviving patients were entered into a Markov model to calculate total costs, number of IFDs and number of life-years gained per patient over a lifetime horizon in each disease and treatment group. Two health states, alive and dead, were considered. Health effects were discounted using a rate of 3%. Univariate and probabilistic sensitivity analyses were conducted. During the first 100 days, posaconazole tablets were associated with a lower risk of IFDs (0.046 vs. 0.111), longer life expectancy (2.92 vs. 2.69 years) and lower total costs (€5906.06 vs. €7847.20 per patient) over the patients' lifetimes compared to FLU or ITRA treatments. Thus, posaconazole tablets were more effective and less costly than FLU or ITRA. Probabilistic sensitivity analysis indicated that there was a 79.9% probability of posaconazole tablets being cost-saving compared to FLU or ITRA. From the Spanish NHS perspective, posaconazole tablets are cost-effective compared to FLU or ITRA in AML or MSD patients with chemotherapy-induced neutropenia and at high risk for IFDs. MSD Sharp & Dohme.