We investigate the impact of the non-zero cosmological constant on the clas
sical decaying dark matter theory developed by the late Dennis Sciama. In p
articular, we concentrate on the change in relevant values of cosmological
parameters in comparison to the high-precision estimates given by Sciama (1
997). It is shown that the appropriate changes in resulting parameter value
s are such to make the DDM concept less plausible. This is in complete agre
ement with recently reported observational results detrimental to this theo
ry.