Graduated from the Lithuanian Art Institute in 1967, teachers Antanas Gudaitis, Vladas Karatajus, Vladas Mackevičius. 1971-1980 lecturer at Vilnius University, since 1980 lecturer at the Lithuanian Art Institute (since 1990 Vilnius Academy of Arts), since 1993 professor, 1995-2000 vice-rector.
In the 1980s, he emerged as a prominent artist together with his colleagues Arvydas Šaltenyas, Algimantas Jonas Kuras, and Algimantas Švėgžda. Forming the informal Grupė 4 group, these artists challenged the uplifting, majestic themes that had prevailed in painting until then. Kostas Dereškevičius was attracted by the banal everyday life of a Soviet man, his everyday life, and his gaze at the signs and fashions of Western culture. Irony and even kitsch are intertwined with sincere admiration in his work. In addition to figurative works, Kostas Dereškevičius painted landscapes, and in the course of time, he increasingly turned towards abstract art.
The artist's work is dominated by urban-themed paintings, which ironically and grotesquely depict everyday life situations and unimaginative objects, such as advertisement poles, posters, windows, trolleybus doors (the series "Windows" 1969-1980, "Van", "Trolleybus" in 1980, "Remains of Posters" in 1985). He painted figurative compositions (cycle "On the Road" 1974-1976), portraits, mostly of women ("Woman with an Umbrella" 1977, "Naturalist O. B." 1980, "Disco Singer" 1984), self-portraits (1968, 1974), landscapes, still lifes, abstract compositions ("Painting with Blue" 1992, "Sneaky Figure" 1993, "Falling Diagonal" 1994). The paintings are emotional, expressive in colour, expressive in drawing, often in flat fragmentary compositions.[4]
Member of the group "24". Since 1966 participated in art exhibitions. Individual exhibitions in Vilnius (1976, 1987, 1995, 2003), Tallinn (1978), Moscow (1986), Mažeikiai (1995), Warsaw (1996).
