In the current paper it is shown that tensile and compression strength of sheets from hardwood high yield pulps (HYP), which has been manufactured at a low energy input in refining, can be multiplied by improving the fibre-fibre bond strength and the number of contact areas between fibre surfaces in the sheet structure. At fibre surface treatment with cationic starch the properties are improved at almost preserved bulk (i.e., preserved density). Remarkable improvements are achieved at densification of the sheet structures by pressing in a hot press nip at temperatures well above the softening temperature of wet lignin. The former technique is above all to prefer in manufacturing of middle plies in paperboard composites, whereas the latter technique is of special interest in manufacturing of packaging papers with high demands upon strength. For instance, it is shown in the paper how tensile index on sheets of CTMP from birch (CSF 480 ml) can be enhanced from 20 to 50 kNm/kg and compression index (SCT) from 10 to 35 kNm/kg by the tested techniques.