Polysulfone composites were prepared by solutioncasting, using various types of treated carbon nanotubes(CNTs) at loadings of up to 5 wt%. The CNTtypes tested were: as-received, acid treated, OCA surfactant,OCA functionalized and Poly(methyl methacrylate)functionalized nanotubes prepared using both asreceivedand acid treated CNT. The treatment typesinvestigated were selected based upon their solubilityparameters and on the results of previous studies.The treated CNTs, CNT/solvent dispersions and thefinal composite samples were characterised using FourierTransform Infrared Spectroscopy (FTIR), thermalanalysis, Transmission Electron Microscopy (TEM),Ultraviolet-Visible (UV-vis) spectroscopy, optical microscopy,electrical conductivity and tensile testing. Itwas observed that the all the treatments studiedimproved the stability of CNT in the solvent. Of theCNT types studied, composites containing OCA functionalisedCNT displayed the lowest percolation threshold(3 wt%) and highest mechanical performance.While the use of Hildebrand solubility parameters isuseful in indentifying promising CNT treatments, theiruse can not fully predict CNT dispersion behaviour andcomposite performance. It is also critical to considerthe influence of any treatments on CNT length and residualsolvent levels.