Various　morphologies　of　cobalt　hydroxides　have　been　successfully　prepared　from　cobalt　nitrate　with　the　assistance　of　dimethylglyoxime　in　water/ethanol　solutions　by　hydrothermal　processing　at　220　°C.　The　crystalline　products　are　hexagonal　phase　of　β-cobalt　hydroxide,　and　the　crystallinity　increases　as　the　volume　ratio　of　water　to　ethanol　rises.　Hexagonal　plate-like,　broom-like　or　straw　bundle-like,　and　grass-like　cobalt　hydroxides　are　obtained　with　water　to　ethanol　ratios　of　1:0,　2:1　and　1:2,　respectively.　The　novel　bundle-like　assemblies　are　further　constructed　from　lots　of　nanobelts,　which　mainly　grow　along　[100]　direction　and　evolve　from　less-crystalline　disc-like　structures　and　semi-crystalline　flower-like　assemblies　as　the　hydrothermal　time　extended.　©　2010　Elsevier　B.V.　All　rights　reserved.