  Spectra of high-metallicity (12+log(O/H) > 8.2) HII regions where oxygen
auroral lines are measurable in both the O+ and O++ zones, have been extracted
from the Data Release 6 of the Sloan Digital Sky Survey (SDSS). Our final
sample consists of 181 SDSS spectra of HII regions in galaxies in the redshift
range from ~0.025 to ~0.17. The t_2,O-t_3,O diagram is examined. In the SDSS
HII regions, the electron temperature t_2,O is found to have a large scatter at
a given value of the electron temperature t_3,O. The majority of the SDSS HII
regions lie below the t_2,O-t_3,O relation derived for HII regions in nearby
galaxies, i.e. the positions of the SDSS HII regions show a systematic shift
towards lower t_2,O temperatures or/and towards higher t_3,O temperatures. The
scatter and shift of the SDSS HII regions in the t_2,O-t_3,O diagram can be
understood if they are composite nebulae excited by two or more ionizing
sources of different temperatures.
