The purpose of this study is to compare perceived room volume and personal area around oneself from reclining postures to actual room dimensions. The perceptions of subjects are reported for survey in a full-scale room with adjustable wall and ceiling-surfaces. The Method of Comparative Judgment was used; each subject was asked to estimate using either the Rating Method or Magnitude Estimation. Subjects judged which room volume was larger or personal area around oneself was wider than others. It is concluded that : 1. In case two rooms were equal in volume, small floor with high ceiling room volume was perceived larger than large floor with low ceiling room volume by the conditions of bed position. 2. Room volume was compared more accurately from reclining postures than standing postures. 3. The judgments factor of personal area around oneself could be classified into "the interval dimension between beds" and "the field surrounding oneself. 4. Perception of room volume was influenced by perception of personal area around oneself. 5. The tendency to perception of room volume and personal area around oneself changed as the interval dimension between beds had become wider.