In this chapter diffusion of magnetic nanoparticles (MNPs) inside a biological tissue as a porous media during magnetic fluid hyperthermia (MFH), has been reviewed. Power dissipation of MNPs in an alternating magnetic field has been explained. Also, the effects of infusion flow rate of MNPs as well as MNPs injection volume on the deposition of MNPs inside the biologicaltissue have been investigated. Moreover, diffusion of MNPs inside the tissue in mono- and multi-site injection inside an irregular biological tissue, have been studied.