The surface segregation in poly(butyl acrylate) (PBA)/poly(vinylidene fluoride-co-hexafluoroacetone) [P(VDF-HFA)] blends was confirmed by X-ray photoelectron spectroscopy (XPS), and is thought to be caused because the surface tension of P(VDF-HFA) is smaller than that of PEA. The PBA/P(VDF-HFA) blends were miscible at room temperature and exhibited a lower critical solution temperature (LCST) phase behavior. Thus, it was considered that the surface segregation of the P(VDF-HFA) component in PBA/P(VDF-HFA) blends was caused by the difference in surface tension between the b components. Depth profiles [In(phi(1)(d)-phi(1)(b)) vs. depth (d), where phi(1)(d) and phi(1)(b) are the volume fractions at 1 depth d from the surface and into the bulk, respectively] for PBA/P(VDF-HFA) blends were constructed by the mean-field treatment. The In(phi(1)(d)-phi(1)(b)) vs. d plots for the PBA/P(VDF-HFA) blends could be approximated by a straight line.