The present invention relates to 2'-Substituted Nucleoside Derivatives of Formula (I): and pharmaceutically acceptable salts thereof, wherein A, B, X, R1, R2 and R3 are as defined herein. The present invention also relates to compositions comprising at least one 2'-Substituted Nucleoside Derivative, and methods of using the 2'-Substituted Nucleoside Derivatives for treating or preventing HCV infection in a patient.