Background: Invasive pulmonary aspergillosis (IPA) is a very severe manifestation of Aspergillus disease. Besides well-known risk groups of deeply neutropenic hematologic and solid organ transplant recipients other risk groups among patients treated in ICUs have been recognized. The prevalence of IPA among ICU-patients is not known and it is not known how well IPA is recognized in ICU-settings. The diagnosis of IPA is often difficult to make and non-invasive ways to diagnose IPA reliably are needed. Objectives: In this study we studied the clinical significance of Aspergillus -positive respiratory samples in ICU-patients. Methods: We retrospectively evaluated the ICU-patients (N = 205) who provided Aspergillus -positive respiratory samples in 2007-2020 and classified patients to groups of “colonization”, “putative IPA”, “proven IPA “, as in AspICU algorithm. Data were collected from laboratory registry and Helsinki University Hospital medical records. Underlying conditions, reasons leading to treatment in ICU, immunosuppression, known risk factors of IA in ICU, signs of infection, results of Aspergillus -specific laboratory testing, use of antifungal treatment, survival, and reason of death were assessed. Results: Majority of the findings (63%) were colonization, 11 (5%) patients had proven IPA, and “putative IPA” 59 (29%) of the patients. All patients with proven IPA died within one year, whereas mortality in putative and colonization groups was 39% and 33% respectively. Difference in mortality during one year between “colonization” and “putative IPA” groups was not statistically significant (p = .244), but when both “proven” and “putative” IPA were included, the difference was statistically significant, p = .019. Overall hospital mortality in the study group was 38%. Mortality in all the groups is higher than overall ICU-patient mortality of non-selected patients in Finland. Conclusions: The overall incidence of Aspergillus -findings in our ICUs was low. Isolation of Aspergillus in critically ill is associated with high mortality irrespective of invasion or colonization.