The packing materials for columns used in reversed phase chromatography (RPC) are substances that bond chemically with alkyl groups and other functional groups as a simple substance of silica gel. The octa decyl group (ODS: Octa Decyl Silyl or C18) and the octyl group (C8) may be mentioned as representative examples. The ODS column is frequently used as the first choice when studying separation conditions, but separation of isomers is inadequate in some cases. Phenyl columns show different separation behavior from ODS columns. Due to the phenyl skeleton, in addition to the hydrophobic interaction, the π-π interaction also contributes to separation in the phenyl column, resulting in higher selectivity for aromatic compounds. This Application News introduces an example of analysis of the positional isomers of cresol by using a phenyl column that displays different separation characteristics from ODS columns.