Length-weight (LW) relationships were estimated and compared for 10 commercially important fish species caught during September-December 2004 from two lagoons in the Ionian Sea based on similar length ranges. The median value of the exponent b of the LW relationships was 3.091 and ranged from 2.444 to 3.536. The larger specimens of the mid-trophic level species (ie Sparus aurata, Diplodus annularis and D. sargus) were heavier at the same length in the less eutrophic lagoon. In contrast, most of the low-trophic level species (ie Mugilidae) did not show significant (P> 0.05) differences of the LW parameters between the studied lagoons. The estimated parameters of the LW relationships for each species between the two lagoons in relation to their trophic state are also discussed. Our findings indicated that the LW relationships of the mid-trophic level species may be possibly used as an index of the trophic state in lagoons.