Diamond-like carbon films, grown on microscope slides by a dual-ion beam sputtering system, were implanted by 110 keV N+ under the doses of 1 x 10(15), 1 x 10(16) and 1 x 10(17) ions cm(-2) respectively. The implantation induced changes in electrical resistivity of the films and in infrared (IR) transmittance of the specimens were investigated as a function of implantation dose. The structural changes of the films were also studied using IR spectroscopy and Raman spectroscopy. It was observed that, with the increase of implantation dose, the diamond-like carbon films display two different stages in electrical and optical behaviours. The first is the increase of both the film resistivity and the IR transmittance of specimen at the dose of 1 x 10(15) ions cm(-2) which, we consider, is attributed to the implantation-induced increase of sp(3) C-H bonds. However, when the doses are higher than 1 x 10(15) ions cm(-2), the film resistivity and the IR transmittance of specimen decrease significantly and the decrease rates at dose range of 1 x 10(16) to 1 x 10(17) ions cm(-2) are smaller than those between 1 x 10(15) and 1 x 10(16) ions cm(-2). We conclude that the significant reductions of the two parameters at high doses are caused by the decreases of bond-angle disorder and of sp(3) C-H bonds, the increases of sp(2) C-C bonds dominated the crystallite size and/or number and also the sp(2) C-H bonds. The smaller decrease rates at a dose range of 1 x 10(16) to 1 x 10(17) ions cm(-2) may be caused by further recombination of some retained hydrogen atoms to carbon atoms.