Aim: Analysis of two cases of IPA with an emphasis on the radiological and pathohistological findings of this entity. Introduction: Aspergillus spp. can cause a wide range of lung diseases, depending on the current state of immunity and the existing pulmonary diseases. Invasive pulmonary aspergillosis (IPA) is severe form of pulmonary mycosis, with the appearance of granulomatous inflammation with the development of necrosis and suppuration, as well as the invasion of hyphae into pulmonary parenchyma and the blood vessels and spreading the disease out of the lungs. Material and Methods: In the five-year period, two cases of IPA were diagnosed at the Institute of Pulmonary Diseases of Vojvodina. Material for pathohistological analysis, obtained by surgical method and on autopsy, was stained with standard H E staining, as well as with special staining methods: PAS and Grocott. Results: Patients were 67 and 48 years old and both were treated for acute lymphoblastic leukemia. They were admitted to our hospital in respiratory insufficiency and severe neutropenia with a radiologically diagnosed IPA based on HRCT finding of “halo sign”. This sign pathohistologically corresponds to foci of necrosis of lung parenchyma surrounded with the zone of hemorrhage. In addition to these foci of necrosis, in the wall and lumen of blood vessels, numerous septate hyphae with dichotomous branching at 45° were found. Conclusion: Although the pathohistological diagnosis is golden standard for diagnosis of IPA, given the invasiveness of the techniques for obtaining material for analysis, diagnosis can be made based on HRCT finding of “halo sign”.