Particleboard was fabricated using hinoki (Japanese cypress: Chamaecyparis obtsusa Endl.) particles and different amounts of diphenylmethane diisocyanate (MDI) resin (2%, 4%, 6%, and 9%) and phenol-formaldehyde (PF) resin (6% and 10.2%). Four accelerated aging treatment tests were conducted to compare the durability performance of MDI-bonded boards with that of PF-bonded boards: two Japanese industrial standard wet-bending tests, a European cyclic moisture test (V313), and the American Society for Testing and Materials (ASTM) six-cycle test (ASTM-6c). The bending strength of the wet MDI boards increased with increasing resin content, and the strength retention after the treatment was greater than 50 percent, which corresponded to that of high-moisture-resistant boards. After the V313 and ASTM-6c treatments, the thickness swelling of the MDI boards with 6 percent resin content was less than 5 percent, whereas that of the PF boards was about 10 percent. The thickness of the specimens varied according to the resin content and at each step of the treatment for both the V313 and the ASTM-6c tests. The resin content equivalence for the two types of resin was determined based on the internal bond (IB) strength after aging treatments of both types of board. The MDI board required only 50 to 70 percent of the resin required for a PF board with a comparable IB quality. The superior performance of the MDI-bonded board was clear after all the tests except for the boiling treatment, in which no significant difference was observed between MDI and PF.