Although numerous carbohydrates play significant roles in mammalian cells, development of carbohydrate-based reagents and therapeutics are hampered by the technical difficulty of chemically synthesizing complex carbohydrate structures. Use of carbohydrate mimetic peptides circumvents this difficulty, as short peptide can be easily synthesized and modified. We as well as others identified carbohydrate mimetic peptides by screening peptide displaying phage library using anti-carbohydrate antibodies and lectins. This review introduces our experiences with I-peptide that was used for identification of new carbohydrate binding receptor expressed in the lung endothelial cells, and those with IF7 peptide that can be used as a therapeutic against malignant tumors.