The effects of varying levels of dietary n-3 highly unsaturated fatty acids (HUFA) and the ratios of docosahexaenoic acid/eicosapentaenoic acid (DHA/EPA) on survival, molting and growth of larval snow crab Chionoecetes opilio were examined in two separate experiments, in which larvae were reared in small containers until reaching the first stage crab. In experiment I, zoea larvae were fed rotifers enriched with n-3 HUFA at three levels, and rotifers without n-3 HUFA enrichment. In experiment II, zoea larvae were fed rotifers enriched with n-3 HUFA at a constant level, which was considered as optimum from experiment I, but having different DHA/EPA ratios, and fed non-enriched rotifers. In both experiments, megalopa larvae were fed non-enriched Artemia sp. Larval survival and growth were improved by feeding rotifers enriched with n-3 HUFA. The occurrence of abnormal moltings during the metamorphosis from megalopa to the first stage crab decreased with increasing n-3 HUFA content in rotifers. The better survival rates from the first zoea stage to the first crab stage were observed when zoeae were fed rotifers containing ∼2.3 g/100 g n-3 HUFA (dry matter basis) with the DHA/EPA ratio of ∼1.5.