Ionic liquids with anions of strong hydrogen-bond basicity have been broadly reported in the literature as effective solvents for the dissolution of the components of lignocellulosic biomass. The key attributes of various ionic liquids are reviewed with a focus on their structural and functional properties related to biomass dissolution capacity. A number of the most studied ionic liquids with high solubility for cellulose and lignin have often been found not suited for catalytic conversions of these biomass components. Metal chlorides in chloride-based ionic liquids are robust catalyst systems for efficient cellulose and lignin conversions. Emerging leads in the literature related to the use of ionic liquids for catalytic conversions of cellulose, cellulosic carbohydrates, and lignin are discussed.