The invention is related to lossless compression of prefix-suffix-codes wherein a prefix comprises unary code, and to corresponding decompression. The method for lossless compressing prefix-suffix-codes comprises the steps of forming a first contiguous bit sequence from the prefixes, and lossless compressing the first contiguous bit sequence by removing redundancy related to the difference between the first value's frequency in the first contiguous bit sequence and the second value's frequency in the first contiguous bit sequence. Bit values are unevenly distributed in the prefixes while distribution of bit values in the suffixes is more even. Therefore, better compression is achievable if the prefixes are compressed separately.