Provided herein is a lens composition of an LED device for an LCD having high transparency and high heat resistance, and an LED device, a backlight unit and an LCD comprising the lens composition. The lens composition includes a copolymer represented by the formula 1 and having a weight average molecular weight of about 5,000 to about 500,000: ##STR00001## wherein R.sub.1 and R.sub.2 independently represent a hydrogen atom, a linear, branched or cyclic alkyl group having 1 to 10 carbon atoms or --COOR.sub.3 group in which R.sub.3 represents a linear, branched or cyclic alkyl group having 1 to 10 carbon atoms, R.sub.4 and R.sub.5 independently represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, the ratio n/n+m ranges from about 0.3 to about 0.995, and the ratio m/n+m ranges from about 0.005 to about 0.7.