The aim of this study is to determine the feasibility of achieving quantitative measurement in (90)Y-microspheres liver selective internal radiotherapy (SIRT) by imaging (90)Y with a conventional non-time of flight (TOF) PET device. Instead of the bremsstrahlung x-rays of the β-decay, the low branch of e(-)- e(+) pair production in the (90)Y-decay was used. The activity distribution in a phantom-simulated liver SIRT was obtained by direct (90)Y-PET imaging. We tested a LYSO TOF PET and two GSO and BGO non-TOF PET scanners using a 3.6-l cylindrical phantom filled with the (90)Y solution containing two sets of hot and cold spheres. The best hot contrast was obtained with the LYSO TOF. It was close to the expected value and remained constant, even for short acquisition times. The LYSO non-TOF was about 10% lower. The GSO performed similarly but degraded for shorter times whilst the BGO was the worst with 40% loss. For the cold spheres, the LYSO TOF and the GSO provided the best results, while the LYSO non-TOF and the BGO were the worst. (90)Y PET imaging in liver SIRT is achievable with LYSO TOF. Conventional LYSO and GSO show a loss of contrast and require longer acquisition times. BGO imaging is not feasible for dosimetry calculation.