We compare subcarrier 4 Pulse Position Modulation (SC-4PPM) with baseband 4 Pulse Position Modulation (BB-4PPM) for visible-light communications when we use an imaging sensor receiver. In visible-light communication systems, background light is a critical factor which affects the performance of communication. We take account of fluorescent lamps driven by conventional ballasts and sunlight as indoor/outdoor background noise sources. On the other hand, the imaging sensor receiver can mitigate the effect of background light. In this paper, we analyze bit error rate (BER) performances of BB-4PPM and SC-4PPM detected by the imaging sensor receiver. Our results indicate that SC-4PPM shows better performance than that of BB-4PPM when resolution is so low that the amplitude of the interference produced by fluorescent lamps is much larger in the indoor environment. We also find that SC-4PPM is not better than BB-4PPM in the outdoor environment.