  We present adaptive-optics (AO) assisted J, H and K/K' images of 8 UCHII
regions taken with the ALFA and ADONIS AO systems at Calar Alto and La Silla
observatories. The images show details of the stellar population and the
near-IR morphology of UCHIIs with unprecedented resolution. We have searched
for the ionizing sources of the regions using near-IR photometry. The spectral
type of the ionizing and most luminous stars inferred from our photometry has
been compared with spectral type estimates from IRAS and published
radio-continuum measurements. We find that the photometric near-IR spectral
types are earlier than estimates from radio and IRAS data. This difference is
alleviated when stellar spherical models including line blanketing and stellar
winds instead of non-LTE plane-parallel models are used to derive the radio-
and IRAS-based spectral types. We also made an attempt to correlate the
properties of the near-IR ionizing population with MSX data and published CS
measurements. No correlation was found. We note that in two of the regions
(G309.92+0.48 and G61.48+0.09B1), the best candidate to ionize the region is
possibly a super-giant.
