We are constructing the world's first 1 mm ³ resolution clinical PET system dedicated to locoregional imaging (e.g. breast, head/neck, etc). The edge-on layout of densely-packed 8×8 arrays of 0.9×0.9×1 mm ³ LYSO crystal elements provides high sensitivity and the capability to position the 3-D coordinates of one or more interactions per 511 keV photon event. Contrast recovery (CR), which measures the accuracy of focal tracer accumulation in the field-of-view (FOV), must be evaluated in order to understand the ability of this system to visualize and quantify smaller lesions. The constructed dual-panel system prototype has a sensitive area of 160mm by 33mm, separated by 64mm. Relative CR was evaluated with the different rod sizes of a micro-Derenzo phantom, yielding CR coefficients of 1.00, 0.96, 1.03, 0.88, 0.67, 0.54 for rod sizes of 4.8, 4.0, 3.2, 2.4, 1.8, and 1.2 mm respectively. A micro hollow spheres phantom scan, with sphere diameters of 7.9, 6.2, 5.0, and 4.0 mm suspended in warm background with an activity concentration ratio of 5:1, resulted in CR coefficients of 0.65, 0.65, 0.61, and 0.54 respectively. Finally, an array of activity-filled capillary tubes were suspended in warm background, with an activity concentration ratio of 20:1, resulting in CR ranging from 0.082 at the center of the FOV to 0.074 at 5 cm away from the center of the FOV. These results show the outstanding performance of our 1mm ³ resolution locoregional clinical PET imaging system at recovering extremely small contrast structures with realistic background uptake values.