Aim: To evaluateroleofdiaphragmaticthickeningandexcursion,assessedultrasonographically,inpre- dicting extubationoutcome. Methods: Fifty-four patientswhosuccessfullypassedspontaneousbreathingtrial(SBT)wereenrolled. They wereassessedbyultrasoundduringSBTevaluatingdiaphragmaticexcursion,diaphragmatic thickness (Tdi)atendinspiration,atendexpirationanddiaphragmaticthicknessfraction(DTF%).Simul- taneously traditionalweaningparameterswererecorded.Patientswerefollowedupfor48hafter extubation. Results: Out of54includedpatients,14(25.9%)failedextubation.Diaphragmaticexcursion,Tdiatend inspiration, atendexpirationandDTF%weresignificantlyhigherinthesuccessfulgroupcomparedto those whofailedextubation(p 0.05).Cutoffvaluesofdiaphragmaticmeasuresassociatedwithsuccess- ful extubationwere≥10.5mmfordiaphragmaticexcursion,≥21mmforTdiatendinspiration,≥10.5mm for Tdiatendexpiration, ≥34.2% forDTF%giving87.5%,77.5%,80%and90%sensitivityrespectivelyand 71.5%, 86.6%,50%and64.3%specificityrespectively.Combiningdiaphragmaticexcursion ≥10.5mmand Tdi atendinspiration ≥21mmdecreasedsensitivityto64.9%butincreasedspecificityto100%.Rapid shallow breathingindex(RSBI)105had90%sensitivitybut18.7%specificity. Conclusion: Ultrasound evaluationofdiaphragmaticexcursionandthicknessatendinspirationcouldbe a goodpredictorofextubationoutcomeinpatientswhopassedSBT.Itisrecommendedtoconsiderthe use oftheseparameterswithRSBIconsequentlytoimproveextubationoutcome.