  We point out the peculiarities of the line of sight of Q0302-003 which was
recently used to estimate the He II opacity at $z \sim 3.285$. This line of
sight contains a large void in Lyman $\alpha$ clouds, in the region used for
the He II opacity observation, and the void is thought to be caused by the
ionizing radiation from a foreground quasar (Dobrzycki and Bechtold 1991). If
this is true, then the radiation from the foreground quasar is more relevant in
the region used for the estimation of the He II opacity than the diffuse UV
background radiation. We argue that in that case the observed opacity should
not be used to put constraint on the diffuse UV background radiation. Using a
typical spectral index of quasars, we estimate that most of the observed He II
opacity must be due to Gunn-Peterson effect and suggest a H I Gunn-Peterson
test along this line of sight. We further discuss the clumpiness of the
intergalactic medium in the vicinity of Q0302-003 as suggested by observations.
