Introduction andObjective. The study aimed to assess the effect of the COVID-19 pandemic and slow cancer burden on the healthcare system of the most frequent cancers in the Subcarpathien and Silesian Provinces of southern Poland in the period 2015-2020. Materials and method. Depersonalized, epidemiological data were obtained from the branches of the National Health Founf of Poland (NFZ) in the Subcarpathian and Silesian Province. The database contained 7,814,870 healthcare services granted to 385,845 patients with disease entities classified as C00-C97, according to the ICD-10. Results. In the period 2015-2020, cancer diseases were diagnosed in 3,445 per 100,000 citizens of the Subcarpathian Province and 5248 per 100,000 citizens of the Silesian Province. The changes in SMR values due to cancer diseases found in the Subcarpathian Province were characterized by temporal and spatial differentiation. In the period 2016-2019, unencumbered by the COVID-19 pandemic, the SMR values had decreased on average by -13.2% in most counties of the Subcarpathian Province, but in 2020 the SMR values decreased by -14.7% compared to 2019. In the Silesian Province, similar to the Subcarpathian Province, the values of SMR decreased in the period 2016-2019 in all counties (with the exception of the town of Piekary Śląskie), on average, by -11.5%. Subsequently, in 2020, a significant reduction of SMR compared to 2019 was observed on average by -7.9%. Conclusions. In 2020, a significant reduction in the diagnosis of patients with cancer was found in the one-year perspective study in both Provinces, which suggests the limitation of availability of the specialistic oncologic healthcare services due to the fight against the COVID-19 pandemic. An increased burden of cancers shortly should be expected. Thus, regional and nationwide screening programmes should be introduced to enable diagnosis at the earliest possible stage.