This　paper　proposes　a　new　approach　for　damage　detection　in　beam-like　structures　with　small　cracks,　whose　crack　ratio　[r　=　Hc/H]　is　less　than　5%,　without　baseline　modal　parameters.　The　approach　is　based　on　the　difference　of　the　continuous　wavelet　transforms　(CWTs)　of　two　sets　of　mode　shape　data　which　correspond　to　the　left　half　and　the　right　half　of　the　modal　data　of　a　cracked　simply-supported　beam.　The　mode　shape　data　of　a　cracked　beam　are　apparently　smooth　curves,　but　actually　exhibit　local　peaks　or　discontinuities　in　the　region　of　damage　because　they　include　additional　response　due　to　the　cracks.　The　modal　responses　of　the　damaged　simply-supported　beams　used　are　computed　using　the　finite　element　method.　The　results　demonstrate　the　efficiency　of　the　proposed　method　for　crack　detection,　and　they　provide　a　better　crack　indicator　than　the　result　of　the　CWT　of　the　original　mode　shape　data.　The　effects　of　crack　location　and　sampling　interval　are　examined.　The　simulated　and　experimental　results　show　that　the　proposed　method　has　great　potential　in　crack　detection　of　beam-like　structures　as　it　does　not　require　the　modal　parameter　of　an　uncracked　beam　as　a　baseline　for　crack　detection.　It　can　be　recommended　for　real　applications.　©　2010　Elsevier　Ltd.　All　rights　reserved.