Simple and inexpensive solution chemistry is applied for decoration/formation CdS nanoparticles on multiwall carbon nanotubes (MWCNT's). Simple ion-by-ion mechanism is utilized for the deposition of CdS nanoparticles on MWCNT's. The size of the nanoparticles is controlled by tuning the preparative parameters which is most favorably based on ion-by-ion mechanism. The use of alkaline medium is completely avoided. Complete decoration of CdS nanoparticles on MWCNT's with cubic structure is observed by structural and surface morphological studies. The photoluminescence spectroscopy shows the two intense luminescence bands, i.e. blue and green, evidencing the presence of small size and agglomerated big size particles of CdS over MWCNT's (size-effect). The modification of MWCNT's with CdS presented in this study opens up new avenues in the design of optoelectronic and light-energy conversion devices. (C) 2012 Elsevier B.V. All rights reserved.