The assessment of tumor parameters derived from F-FDG PET/CT in oncology provides valuable information in non-small cell lung cancer. A proper segmentation should delineate tumor with high accuracy, being the most important step to measure metabolic parameters. However, there is still no consensus about the optimal methodology. Additionally, some clinical conditions inherently tied to tumor and imaging can limit the proper tumor delineation. We present some practical cases that represent different aspects to consider during segmentation of primary non-small cell lung cancer by using F-FDG-PET/CT and some possible solutions to tackle with the most common limitations in clinical practice.