fMRI is widely used and seen as the gold standard in non-invasive in-vivo brain imaging. However, due to its technology, it is comes with certain limitations in participant groups and experiments. fNIRS is portable, easy to use and can be applied in subjects of all ages. Hence, it can provide a valid alternative to fMRI in many applications. In this blogpost we discuss advantages that fNIRS has over fMRI, considerations that should be kept in mind and we highlight literature using fNIRS and fMRI to compare, or get complementary information.