Winter hardiness of grasses depends mainly on their frost tolerance and resistance to snow mould pathogens. Many authors reported the main role of soluble carbohydrates in cold-induced resistance to frost or fungi. The accumulation of hexoses activates hexokinase, key sugar-sensing enzyme that initiates a signal transduction process that could be a signal to production of PR (pathogenesis-related) proteins. High levels of sugars influence the osmotic potential of plant tissues and can this way limit their colonization by fungi. Under cold treatment changes in cell wall structure and accumulation of polysaccharides and lignin in cell walls can also develop. The strengthening of cell walls limits tissue penetration by fungal mycelium and decreases efflux of water from cells under osmotic stresses. In performed studies accumulation of soluble carbohydrates and phenolics in Lolium-Festuca introgression forms and androgenic forms derived from two Festulolium cultivars ‘Felopa’ and ‘Sulino’ was analysed. The plants were chosen to studies after field selection in winter conditions in Łopuszna. On the basis of the observed changes in sugar content the studied forms were compared with parent species and divided into three groups: group-accumulating soluble carbohydrates like Lolium and like Festuca; the third group was called ‘mixed type’. The winter hardiness and resistance to snow mould in the field conditions, laboratory frost tolerance and changes in the sugar content were analysed. The introgression forms of Festuca type were characterised by better winter hardiness and higher frost tolerance than plants of Lolium type. The forms derived from Festulolium cv. ‘Sulino’ were more tolerant to frost and winter conditions than genotypes derived from cv. ‘Felopa’. Large differences in phenolic compound accumulation were observed among the analysed forms. However, this parameter was not correlated with the winter hardiness of plants. Similarly, no direct influence of soluble carbohydrate and phenolic compound content on plant resistance to snow mould was found.