The present study aims at getting more insight on the unclear ties between cellulose DP and fibres strength. The assumption that ECF pulps perform better than TCF pulps have led many to believe that ozone TCF cannot compete with ECF bleaching ). In fact, the absence of scientific consensus on ozone-bleached fibres mechanical quality hitherto represents a significant obstacle to the industrial implementation of water-saving and less polluting bleaching processes such as TCF bleaching.