The invention concerns a decoding method with flexible input and flexible output of a linear block code word (s) of dimension k and length n, received from a transmission channel, comprising steps which consists in: generating a list of firm words ( u b) of the code close to the received code word ( s ), by coding a list of k-uplets obtained by firm approximation of the received word components and by changing the less reliable components; computing the j output flexible word component by difference between the generated closest word metrics, and the generated closest word having an opposite j component, or in default the generated least close code word. The invention also concerns an iterative method for decoding a product code word received on a transmission channel, using such decoding method with flexible input and flexible output. It enables quick and efficient decoding of a code product words, even if there is no algebraic decoder.