Canopy light interception is fundamental factor contributing to horticultural crop performance and quality. No studies have evaluated light interception of modern fruit tree architectures such as compact fruiting walls. Herein we report on daily trends in Photosynthetically active radiation (PAR) interception in sweet cherry trees trained to vertical (upright fruiting offshoots (UFO)) and angled (Y-trellised) fruiting wall architectures using a new developed mobile sensor system. PAR levels at ca. 35 cm above the soil surface were determined every 2 hours on one day in early July 2011 from 0700 to 1900 hr, and compared with levels under clear sky. Two North-South rows from each architecture were tested. The average of daily light interception (LI%) by the canopies for ‘Y’ trellised trees was 82%, higher than that for UFO, 60%. Difference between architectures increased between sunrise and noon from 4.6% to 51.4%, and then decreased to 3.5% at sunset. Further, UFO architecture had greater variation of light interception throughout the day than Y-trellised architecture did, with standard deviations 0.28 and 0.093, respectively. Our results suggest that, for Y-trellised architecture, light interception values between 900 HR and 1100 HR, or between 1500 HR and 1700 HR are representative of daily interception. For UFO architecture, the representative light interception values are between 900 HR and 1100 HR, or 1300 HR and 1500 HR.