A 58-year-old woman who underwent surgery for breast cancer experienced recurrence in the ipsilateral breast during follow-up after postoperative radiotherapy and was scheduled for additional mastectomy. An 81-year-old man was found to have bilateral lung cancer during follow-up after coronary artery bypass grafting. Both patients underwent diffusion-weighted whole-body imaging with background suppression (DWIBS) for whole-body cancer screening, which led to incidental detection of bladder cancer that was adequately treated. In both cases, the lesions were unlikely to have been detected using positron emission tomography/computed tomography (PET/CT). This suggested that DWIBS might be more useful than PET/CT for whole-body cancer screening.