Abstract INTRODUCTION Diffusion Weighted Whole Body Imaging with background body signal Suppression (DWIBS) is an imaging technique that encompasses comprehensive imaging of the entire body through diffusion-weighted imaging (DWI). In recent years, it has been increasingly utilized for investigating the etiology of fever or primary cancer. Here we present two cases of DWIBS for searching for primary cancer in patient with intracranial metastasis. CASE PRESENTATION Case1: A 60-year-old man presented with headache and diplopia and was admitted to our hospital. MRI revealed a tumor in the clivus exhibiting contrast enhancement. Endoscopic transsphenoidal surgery confirmed the diagnosis of squamous cell carcinoma. DWIBS demonstrated high intensity in a region similar to the esophagus seen on contrast-enhanced CT, leading to the diagnosis of brain metastasis from esophageal cancer. Case 2: A 50-year-old man presented with left facial paralysis and left hemiplegia and was admitted to our hospital. MRI revealed a tumor in the right middle frontal gyrus. Craniotomy confirmed the diagnosis of adenocarcinoma. Although the primary cancer remained unidentified upon initial examination, subsequent investigations revealed it originated from the lung. DWIBS showed high intensity in a region similar to the lung. DISCUSSION While FDG-PET is commonly utilized for cancer detection, its invasiveness and limitations prompt consideration of alternative modalities such as DWIBS. Recently there are some studies that have shown DWIBS to be superior to FDG PET in detecting esophageal and lung cancers. Thus, DWIBS may serve as a viable option for primary cancer screening in hospitals or communities where access to FDG PET is limited. CONCLUSION Its non-invasive nature makes DWIBS an appealing option for primary cancer detection, and further advancements are anticipated.