The invention relates to a ply of a linerboard for corrugated board, which ply exhibits high strength properties and which enables the production of lightweight linerboards. The ply of the invention comprises 20-80 wt % CTMP from wood fibers and 80-20 wt % chemical pulp, calculated on the total fiber weight of said ply and strength additives chosen from the group of microfibrillated cellulose (MFC), anionic or cationic polymers and starchor combinations thereof. The ply exhibits a geometric SCT index of above 22 Nm/g and a density of below 680 kg/m3, preferably of below 650 kg/m3.