Introducing: Non-specific uptake in heart, bowel or gut hardly depends on age, fastening period, blood glucose levels. Among all those non-specific uptake levels, liver SUV is often used as a reference point. In our study standard uptake value in liver parenchyma is compared with SUV of lesions suspected for malignant disease. Clinical experience indicates that SUV values in the liver differ to a large extent. Because of this fact there is a question if introducing the correction factor of SUV value in liver is necessary. Materials and methods: One hundred patients were enrolled into the study. There were 46 male and 54 female with the mean age 47 years. Each patient had PET-CT acquisition after 18F-FDG injection. The SUV values were calculated for each ROI (region of interest containing non-specific uptake in liver). The correlation between physiological variables and SUV values in healthy liver was calculated in order to decide if there was a necessity of introducing the correction factor of SUVliv and from which time point from injection to acquisition it should be done. Results: No correlation was found between the height and the SUVliv and between the plasma glucose level and the SUVliv. A rather weak correlation was stated in the case of the weight, the BMI and the time from 18F-FDG injection to acquisition. According to our study there is a need to use a correction factor in cases when the time between injection and acquisition is longer than 80 minutes. Conclusions: The time which elapsed from the moment of tracer injection to acquisition start is very important. Knowing the relationship between this time and obtained SUVliv and proper using of correction factor in the correct time range can be beneficial for identification of putative liver metastases.