The invention relates to a process for treating cellulose fibres which process comprises the steps of providing a slurry comprising cellulose fibers, adding anionic polyacrylamide (A-PAM) with high molar mass to the slurry in a first step and subjecting the slurry comprising fibers and A-PAM to a mechanical treatment in a second step thereby forming a composition comprising microfibrillated cellulose. The invention further relates to a composition produced according to the process.