A compound having a structural formula wherein ring is selected from the group consisting of R 0, independently, is selected from the group consisting of C 1-6 alkyl, C 1-6 heteroalkyl, C 2-6 alkenyl, C 1-6 perfluoroalkyl, C 1-6 perfluoroalkoxy, aryl, heteroaryl, C 3-10 cycloalkyl, C 3-8 heterocycloalkyl, C 1-6 alkylenearyl, C 1-6 alkyleneheteroaryl, C 1-6 alkyleneheterocycloalkyl, C 1-6 alkylenecycloalkyl, OR b, halo, N(R b) 2, SR b, SOR b, SO 2 R b, CN, C(=O)R b, OC(=O)R b, C(=O)OR b, C 1-6 alkyleneN(R b) 2, C 1-6 alkyleneOR b, C 1-6 alkyleneSR b, C 1-6 alkyleneC(=O)OR b, C(=O)N(R b) 2, C(=O)NR b C 1-6 alkyleneOR b, OC 1-6- alkyleneC(=O)OR b, OC 1-6 alkyleneN(R b) 2, OC 1-6 alkyleneOR b, OC 1-6 alkyleneNR b C(=O)OR b, NR b C 1-6 alkyleneN(R b) 2, NR b C(=O)R b, NR b C(=O)N(R b) 2, N(SO 2 C 1-6 alkyl) 2, NR b (SO 2 C 1-6 alkyl), nitro, and SO 2 N(R b) 2; m is an integer 0, 1, 2, 3, or 4; R a, independently, is selected from the group consisting of hydrogen, C 1-6 alkyl, C 2-6 alkenyl, C 1-6 heteroalkyl, aryl, heteroaryl, C 3-8 Cycloalkyl, C 3-10 heterocycloalkyl, C 1-6 alkylenearyl, C 1-6 alkyleneheteroaryl, C 1-6 alkyleneC(=O)OR b, C 1-6 alkyleneC(=O)R b, C 1-6 alkyleneC(=O)N(R b) 2, C(=O)R b, C(=O)N(R b) 2, C(=O)OR b, CN, OR b, halo, N(R b) 2, SR b, SOR b, SO 2 R b, CF 3, OCF 3, NO 2, OC(=O)R b, OC 1-6 alkyleneC(=O)OR b, C 1-6 alkyleneOC 1-6 alkyleneC(=O)OR b, C(=O)NR b SO 2 R b, C(=O)C 1-6 alkylenearyl, C 1-6 alkyleneN(R b) 2, C 1-6 alkyleneOR b, C 1-6 alkyleneSR b, C(=O)NR b C 1-6 alkyleneOR b, OC 1 -6alkyleneN(R b) 2, OC 2-6 alkyleneOR b, OC 2-6 alkyleneNR b C(=O)OR b, NR b C 1-6 alkyleneN(R b) 2, NR b C(=O)R b, NR b C(=O)N(R b) 2, N(SO 2 C 1-6 alkyl) 2, NR b (SO 2 C 1-6 alkyl), SO 2 N(R b) 2, and OSO 2 CF 3; R b, independently, is selected from the group consisting of hydrogen, C 1-6 alkyl, C 1-6 heteroalkyl, C 1-6 alkyleneNH 2, C 1-6 alkyleneNH(C 1-6 alkyl), C 1-6 alkyleneN(C 1-6 alkyl) 2, C 1-6 alkyleneNH(C 1-6 alkyl) 2, C 1-6 alkyleneOH, C 1-6 alkyleneOC 1-6 alkyl, C 1-6 alkyleneSH, C 1-6 alkyleneSC 1-6 alkyl, aryl, heteroaryl, C 3-8 cycloalkyl, and C 3-10 heterocycloalkyl; Y is selected from the group consisting of C(=O)aryl and C 1-6 alkylenearylene, Z is C(=O)N(R c)OH, R c is hydrogenor a pharmaceutically acceptable salt, or hydrate thereof for the use in the treatment of a disease or condition wherein inhibition of HDAC provides a benefit to an individual in need thereof by administering a therapeutically effective amount of the compound. R 0, independently, is selected from the group consisting of C 1-6 alkyl, C 1-6 heteroalkyl, C 2-6 alkenyl, C 1-6 perfluoroalkyl, C 1-6 perfluoroalkoxy, aryl, heteroaryl, C 3-10 cycloalkyl, C 3-8 heterocycloalkyl, C 1-6 alkylenearyl, C 1-6 alkyleneheteroaryl, C 1-6 alkyleneheterocycloalkyl, C 1-6 alkylenecycloalkyl, OR b, halo, N(R b) 2, SR b, SOR b, SO 2 R b, CN, C(=O)R b, OC(=O)R b, C(=O)OR b, C 1-6 alkyleneN(R b) 2, C 1-6 alkyleneOR b, C 1-6 alkyleneSR b, C 1-6 alkyleneC(=O)OR b, C(=O)N(R b) 2, C(=O)NR b C 1-6 alkyleneOR b, OC 1-6- alkyleneC(=O)OR b, OC 1-6 alkyleneN(R b) 2, OC 1-6 alkyleneOR b, OC 1-6 alkyleneNR b C(=O)OR b, NR b C 1-6 alkyleneN(R b) 2, NR b C(=O)R b, NR b C(=O)N(R b) 2, N(SO 2 C 1-6 alkyl) 2, NR b (SO 2 C 1-6 alkyl), nitro, and SO 2 N(R b) 2; m is an integer 0, 1, 2, 3, or 4; R a, independently, is selected from the group consisting of hydrogen, C 1-6 alkyl, C 2-6 alkenyl, C 1-6 heteroalkyl, aryl, heteroaryl, C 3-8 Cycloalkyl, C 3-10 heterocycloalkyl, C 1-6 alkylenearyl, C 1-6 alkyleneheteroaryl, C 1-6 alkyleneC(=O)OR b, C 1-6 alkyleneC(=O)R b, C 1-6 alkyleneC(=O)N(R b) 2, C(=O)R b, C(=O)N(R b) 2, C(=O)OR b, CN, OR b, halo, N(R b) 2, SR b, SOR b, SO 2 R b, CF 3, OCF 3, NO 2, OC(=O)R b, OC 1-6 alkyleneC(=O)OR b, C 1-6 alkyleneOC 1-6 alkyleneC(=O)OR b, C(=O)NR b SO 2 R b, C(=O)C 1-6 alkylenearyl, C 1-6 alkyleneN(R b) 2, C 1-6 alkyleneOR b, C 1-6 alkyleneSR b, C(=O)NR b C 1-6 alkyleneOR b, OC 1 -6alkyleneN(R b) 2, OC 2-6 alkyleneOR b, OC 2-6 alkyleneNR b C(=O)OR b, NR b C 1-6 alkyleneN(R b) 2, NR b C(=O)R b, NR b C(=O)N(R b) 2, N(SO 2 C 1-6 alkyl) 2, NR b (SO 2 C 1-6 alkyl), SO 2 N(R b) 2, and OSO 2 CF 3; R b, independently, is selected from the group consisting of hydrogen, C 1-6 alkyl, C 1-6 heteroalkyl, C 1-6 alkyleneNH 2, C 1-6 alkyleneNH(C 1-6 alkyl), C 1-6 alkyleneN(C 1-6 alkyl) 2, C 1-6 alkyleneNH(C 1-6 alkyl) 2, C 1-6 alkyleneOH, C 1-6 alkyleneOC 1-6 alkyl, C 1-6 alkyleneSH, C 1-6 alkyleneSC 1-6 alkyl, aryl, heteroaryl, C 3-8 cycloalkyl, and C 3-10 heterocycloalkyl; Y is selected from the group consisting of C(=O)aryl and C 1-6 alkylenearylene, Z is C(=O)N(R c)OH, R c is hydrogenor a pharmaceutically acceptable salt, or hydrate thereof