This　paper　considers　single-machine　scheduling　problems　with　group　technology　(GT).　We　consider　the　case　of　group　setup　times　and　job　processing　times　are　a　decreasing　function　of　their　starting　time.　We　first　prove　that　the　makespan　minimization　problem　remains　polynomially　solvable　under　the　general　decreasing　linear　deterioration.　We　then　prove　that　the　total　weighted　completion　time　minimization　problem　remains　polynomially　solvable　under　the　proportional　decreasing　linear　deterioration.