The use of Silicon Photomultipliers (SiPMs) as photon detectors in Positron Emission Tomography (PET) modules offers significant advantages over conventional light sensors, including application in a magnetic field, better resolution and easier operation. Two PET modules have been constructed by coupling 4 x 4 arrays of LYSO sctintillation crystals of area 4.2 x 4.2 mm2 and length 20 mm to SiPMs. Two types of SiPM have been tested: the Hamamatsu S10931-100P and Photonique PCB-PET07 of active surface areas 3 x 3 mm2 and 2.1 x 2.1 mm2 respectively. The energy resolutions, signal pulse properties and energy response of the arrays are presented in view of arrangement into a larger module. Additionally, the surface sensitivity and time resolutions of smaller 1 x 1 mm2 SiPMs from the same manufacturers have been analysed.