The field of imaging science is growing immensely, with the emergence of “noninvasive” in vivo imaging technologies and imaging probes like Positron Emission Tomography (PET), Fluorescence Imaging (FI) and Magnetic Resonance Imaging (MRI), to observe events at molecular and cellular levels, and consequently to speed up drug development processes. For instance, the imaging of cancer specific molecular targets ought to permit precocious diagnosis and superior evaluation to oncology patients. Porphyrins and their derivatives (or related compounds, like phthalocyanines) represent one of the oldest, most widely studied chemical structures, both in nature and in biomedical applications. They display intrinsic affinity for tumor localization and their well-portrayed photophysical and photosensitizing properties can lead to their potential use as sensitizer in a variety of in vivo imaging technologies. This contribution will review recent developments involving tetrapyrrolic -based sensitizers for cancer detection, with emphasis on PET, FI and MRI technologies.