Synchrotron radiation x-ray diffraction measurement was performed to investigate the size effect in ferroelectric nanosized (Pb(0.7)Sr(0.3))TiO(3) particles with various sizes ranging from 10 to 200 nm. The 200 and 002 Bragg reflections were separated using low energy synchrotron radiation x-rays. The peak profiles of the 002 reflections show a large broadening and asymmetry for all particle sizes compared with those of the 200 reflections. These anomalously wide and asymmetric peak profiles become marked for peaks with a large l. The aspect ratio of the lattice constants c/a and the atomic distance between the anions and cations decrease gradually in the vicinity of the surface of the particles, indicating that the asymmetrical profiles can be attributed to the formation of a gradational system.