Presents a high-resolution detector for small animal SPECT and the scintigraphic examination of human extremities or scintimammography. The system consists of a 2 mm NaI (T1) disk coupled to a 5" position sensitive photomultiplier (Hamamatsu, R3292) and an ultra high-resolution, parallel-hole collimator. The usable FOV of this detector has a diameter of 90 mm. The intrinsic spatial resolution is 1.4 mm FWHM and the energy resolution at 140 keV amounts to 8.7%. The system resolution is 1.8 mm FWHM close to the collimator and 2.5 mm at 30 mm source distance with a system sensitivity of 8.8 cps/MBq. Using an iterative reconstruction algorithm the tomographical resolution (in water) amounts to 2.7 mm. When using a pinhole collimator (1.1 mm aperture) the system resolution at 30 mm improves to 1.4 mm and the sensitivity increases by a factor of 3.2 to an absolute value of 27.9 cps/MBq.