The average radii of gyration [R-g] and hydrodynamic radii [R-h] of a set of deuterated polystyrene (DPS) standards with different molar masses in cyclohexane around its Theta-temperature were precisely measured by using static and dynamic laser light scattering. On the basis of these values, the moan segment size (l = 0.331 nm) and chemistry-dependent constant (v(T) = 1.10) used in the renormalization group theory were calculated. In comparison with a normal polystyrene (PS), DPS has a smaller/and a larger v(T). The smaller/indicates that at the Theta-temperature a DPS chain has a smaller conformation (i.e., coils more) than a PS chain with the same contour length, The larger v(T) indicates that in a good solvent a DPS chain extends more than a PS chain for a given increase of the reduced temperature (T - Theta)/Theta. Our results showed that the difference in thermodynamics also leads to an opposite and different temperature dependence of the hydrodynamic radius [R-h] for DPS and PS in cyclohexane.