The purpose of this study was to assess the in vivo efficacy of a cosmetic formulation containing plant extracts including orchid extracts, compared to 3% vitamin C derivative formulated with the same excipient, in Japanese female adult volunteers with melasma and/or lentigo senilis. The ethics committee of Osaka National Hospital approved the protocol of the study. Before recruitment, selection and inclusion of a volunteer in this study, signed informed consent was obtained from each volunteer after she was given clear and precise information on the study, enabling her to appreciate the aim of the study and the consequences of her consent. Forty-eight female volunteers aged 30-60 years applied the plant extracts and vitamin C derivative to one side of the face. After repeated application for 8 weeks, efficacy was evaluated clinically by colorimetric measurements and subjectively using a questionnaire. After 8 weeks of treatment, both the clinical evaluations by a dermatologist and the questionnaire surveys by volunteers indicated that the cosmetic formulation containing plant extracts was significantly effective in improving the size, brightness, color intensity, clarity, visibility and global appearance of the pigmented spots, and also the luminosity complexion and skin clarity of the face. The good agreement between the results of clinical evaluations and those of questionnaire surveys showed that the orchid-rich plant extracts possess efficacy similar to vitamin C derivative in whitening the skin as well as melasma and lentigo senilis on the face of Japanese women.