This article discusses the partial-volume effect (PVE) in PET tumor imaging, emphasizing its impact on the accuracy of tracer uptake measurements. PVE, which refers to the blurring of intensity values in images due to the finite spatial resolution of the imaging system, can significantly bias the measured uptake values, especially in small tumors. The authors review the parameters that influence PVE, such as tumor size, shape, surrounding tissues, and spatial resolution, and describe various methods to correct for PVE. These methods include the Recovery Coefficient (RC), Geometric Transfer Matrix (GTM), deconvolution, partition-based correction, multiresolution approaches, fitting methods, and kinetic modeling. The practical impact of PVE correction is highlighted through studies showing that accounting for PVE can reveal hidden relationships and improve the discrimination between benign and malignant lesions. The article concludes by discussing the potential benefits of PVE correction in therapeutic follow-up and the need for further research to develop more robust and practical correction methods.This article discusses the partial-volume effect (PVE) in PET tumor imaging, emphasizing its impact on the accuracy of tracer uptake measurements. PVE, which refers to the blurring of intensity values in images due to the finite spatial resolution of the imaging system, can significantly bias the measured uptake values, especially in small tumors. The authors review the parameters that influence PVE, such as tumor size, shape, surrounding tissues, and spatial resolution, and describe various methods to correct for PVE. These methods include the Recovery Coefficient (RC), Geometric Transfer Matrix (GTM), deconvolution, partition-based correction, multiresolution approaches, fitting methods, and kinetic modeling. The practical impact of PVE correction is highlighted through studies showing that accounting for PVE can reveal hidden relationships and improve the discrimination between benign and malignant lesions. The article concludes by discussing the potential benefits of PVE correction in therapeutic follow-up and the need for further research to develop more robust and practical correction methods.