The paper focuses on two problems: 1) analysis of bitrate contribution of I and B frames in encoded HEVC data stream, and 2) analysis of distribution of HEVC syntax elements in I and B frames. The relationship between sizes of I and B frames located at a different levels in hierarchical coding scheme was experimentally determined, as well as contribution of HEVC syntax elements in encoded streams of I, B0, B1, B2, and B3 frames. The results are presented in the paper. All presented results concern a wide range of QP values in a video encoder.