  We present UBVRI photometry of three symbiotic stars ZZ CMi, TX CVn and AG
Peg carried out from 1997 to 2008 in Piwnice Observatory near Torun. To search
orbital periods of these stars Fourier analysis was used. For two of them, TX
CVn and AG Peg, we have confirmed the earlier known periods. For ZZ CMi we
found a relatively short period 218.59 days. Assuming, that the orbital period
is twice longer (P=437.18 days), the double sine wave in the light curve can be
interpreted by ellipsoidal effect.
