To investigate the disintegration of wet- and dry-compressed orally disintegrating (OD) tablets, with synchrotron radiation as the X-ray source. Pharmaceutical tablets are vital for the treatment of various diseases. Therefore, they are constantly developed to ensure desirable characteristics. In particular, OD tablets need to disintegrate immediately after absorbing saliva. How these tablets absorb saliva is key to enhancing rapid product development. Recently, absorption processes have been investigated using various noninvasive techniques, including X-ray radiography and X-ray computed tomography. However, X-ray radiography studies on how water without a contrast agent is absorbed, moves, and causes a tablet to swell are scarce. The use of a contrast agent is associated with some shortcomings, including complex data analysis in some instances, alterations in the viscosity of water, and potential influence on fluid transport inside the tablet, thus possibly affecting the disintegration process. Real-time X-ray radiography was used to monitor the disintegration of various tablets, while X-ray computed tomography and software were used to create 3 D images. We demonstrated how pure water penetrated the wet-compressed tablet faster than inside the dry-compressed tablet, and how the latter swelled more. X-ray computed tomography showed the presence of voids in the tablets following water absorption. Our methods are promising for nondestructive fluid absorption and transport investigations inside OD tablets.