Diffractive scintillations from large-scale irregularities of the interstellar medium were observed for 5 strong pulsars at 102.7 MHz. The shifts of the time cross-correlation function of intensity variations at different longitudes of the profile were obtained as a function of longitude separation (phase curve). The shift is defined by the transverse separation of the pulsar emission sources. The maximum values of the spatial separation are: 1-2 x 108 cm. We show that the phase curves are inconsistent with the dipole model of the magnetosphere and change from day to day not only in amplitude, but also in direction.