PET is the only clinically proven method for hadron-therapy monitoring. This method uses imaging of the positron emitting isotopes produced during patient irradiation in hadron-therapy. To maximize the count rates in-beam PET is the preferred option, which requires partial ring configuration. Usage of partial ring PET system causes image artifact and low quality image due to incomplete data. The Time-of-flight (TOF) information provides better image quality for partial ring PET systems. Therefore, PET system with very good time and spatial resolution is necessary for hadron-therapy monitoring. The Resistive-Plate-Chambers (RPCs) providing very good time and spatial resolution might be used for the quality control of hadron-therapy. The objective of this study is the comparison of the performance of two TOF-PET systems, one multi-gap RPC (mRPC) system currently under investigation by the TERA group and a commercially available scintillator-based PET system (Philips GEMINI TF) in order to analyze their feasibility of being applied to monitor cancer treatment with ion- and proton-beams. Various Monte-Carlo simulations were performed using GATE to evaluate the performance of the both systems following NEMA protocols. Furthermore, a set of sources emulating the annihilation photons from β+-emitters produced after proton irradiation on a PMMA target were employed to study the capability to reproduce the proton beam path and the distal edge. Finally, we calculated the activity distribution produced on the basis of one field of the treatment plan for one patient data. The results obtained indicate that mRPC system is not suited for hadron therapy monitoring due to its low sensitivity. On the other side, the Philips GEMINI TF does not provide convincing results either, thus other configurations are still under investigation.