This article describes a new perceived whiteness index, C/V index, which focuses on the brightness-enhancement effect of color components included in the spectral reflectance factor distribution of approximate white objects or in the spectral power distribution of illuminations. The index is developed on the basis of a color vision model. The perceived whiteness of 18 approximate white samples was evaluated, and then a predictability of the index was compared with 17 types of existing whiteness indices. As a result, the C/V index was one of the indices indicating the best predicting performance. The aforementioned findings show that the C/V index is effective in evaluating the perceived whiteness of approximate white objects and the brightness-enhancement effect of color components is an important factor in determining the perceived whiteness. (C) 2009 Wiley Periodicals, Inc. Col Res Appl, 35, 410-418, 2010; Published online 10 November 2009 in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/col.20551