Halibut and flounders differ in size, scales, teeth and the way in which they lie on the ocean floor. Halibut and flounders are both flatfish, but they are only distantly related within that taxon. They are often mistaken for one another.
Halibut are the largest of the flatfish, with some individuals living 55 years and growing to over 500 pounds. Halibut have relatively smooth skin that obscures their scales, and their teeth tend to be concealed deep inside their mouths. Flounders are smaller and have coarser scales and more prominent teeth than halibut.
Halibut are almost exclusively right-eyed, which means that the adults of the species lie flat with their left sides to the sea floor. Flounders show less of a side preference, but they generally lie on their right sides. This lack of conformity among flounders is possibly due to the fact that "flounder" is a group name assigned to loosely related species of the suborder Pleuronectoidei.
The distinction between these two groups is important to commercial fishers because the halibut is an important game fish and is sought after by seafood distributors. However, some species of flounder are generally regarded as inedible due to the difficulty of preparing their meat and unpleasant taste.