A coding and modulation apparatus and method are presented. The apparatus (10) comprises an encoder (11) that encodes input data into cell words, and a modulator (12) that modulates said cell words into constellation values of a non-uniform constellation. The modulator (12) is configured to use, based on the total number M of constellation points of the constellation and the signal-to-noise ratio SNR in dB, a non-uniform constellation from a group of constellations comprising one or more of predetermined constellations defined by the constellation position vector w0 . . . b−1, wherein b=M/4.