Stereotactic body radiation therapy (SBRT) is gaining wide acceptance as a treatment modality for lung and liver tumors, and it is crucial to make an accurate evaluation of the local effects of ablative doses of radiation in terms of local tumor control and normal tissue reaction or damage. The very complex radiation dose distribution of SBRT, the use of a large number of non-opposing and noncoplanar beams, and the delivery of individual ablative doses of radiation may cause substantially different radiographic appearance on diagnostic imaging compared with conventional radiation therapy. Different patterns of radiographic changes have been observed in the lung and liver after SBRT. This article reviews the post-SBRT imaging changes in the lung and liver. Since computed tomography and PET are the most commonly used diagnostic imaging tools for monitoring lung tumor and computed tomography for liver tumors, this article will focus on the changes observed on those imaging modalities.