  We report on observations of a solar prominence obtained on 26 April 2007
using the Extreme Ultraviolet Imaging Spectrometer on Hinode. Several regions
within the prominence are identified for further analysis. Selected profiles
for lines with formation temperatures between log(T)=4.7-6.3, as well as their
integrated intensities, are given. The line profiles are discussed. We pay
special attention to the He II line which is blended with coronal lines. Our
analysis confirms that depression in EUV lines can be interpreted by two
mechanisms: absorption of coronal radiation by the hydrogen and neutral helium
resonance continua, and emissivity blocking. We present estimates of the He II
line integrated intensity in different parts of the prominence according to
different scenarios for the relative contribution of absorption and emissivity
blocking on the coronal lines blended with the He II line. We estimate the
contribution of the He II 256.32 line in the He II raster image to vary between
~44% and 70% of the raster's total intensity in the prominence according to the
different models used to take into account the blending coronal lines. The
inferred integrated intensities of the He II line are consistent with
theoretical intensities obtained with previous 1D non-LTE radiative transfer
calculations, yielding a preliminary estimate for the central temperature of
8700 K, central pressure of 0.33 dyn/cm^2, and column mass of 2.5 10^{-4}
g/cm^2. The corresponding theoretical hydrogen column density (10^{20} cm^{-2})
is about two orders of magnitude higher than those inferred from the opacity
estimates at 195 {\AA}. The non-LTE calculations indicate that the He II 256.32
{\AA} line is essentially formed in the prominence-to-corona transition region
by resonant scattering of the incident radiation.
