Modern furniture is mostly made of panel products such as a glue-up panel, a particle board and a medium density fiberboard(MDF). Warping is a major defect of these panel products resulting in degrading final products. In this study the factors related to the warping of a glue-up panel and MDF were investigated by comparing the physical properties of warped specimens with those of the unwarped. The differences between the moisture contents measured on the both surfaces of specimens were found to mainly influence the warping of glue-up panel specimens whether conditioned or not. The average oven-dry density of warped glue-up panel specimens was definitely higher than that of the unwarped at l% significance level. For MDF the influencing factor on warping has not been revealed yet, however it was found that the conditioning reduced the number of warped specimens.