Abstract: Background: The master's thesis explored the influence of reconstruction parameters (which include inputs to iterative algorithms, additional functions such as PSF) on the qualitative and quantitative characteristics of diagnostic PET images.Aims of the study: The aim of the master's work is to assess the influence of reconstruction parameters on the qualitative and quantitative characteristics of diagnostic images.Methods:The master's thesis was carried out using a combined PET-CT scanners manufactured by General Electrik (Discovery 710 and two Discovery I. As part of the study, an experiment was performed using a water-filled IEC phantom with six installed spheres of different diameters. This phantom is a model of pathological foci of accumulation of a radiopharmaceutical against the background of physiological accumulation of a radiopharmaceutical (for example, liver metastases). An analysis of the effect of reconstruction parameters was also performed based on real patient studies. Optimal scanning parameters are presented that allow performing studies without losing diagnostic information