A modification of the Slater's atomic orbital theory (AOT) is
presented in this paper and applied to the calculation of energies
for (1$sns$)$^1S^e$, (1$snp$)$^1P^o$, (1$snd$)$^1D^e$ and
($ns^2$)$^1S^e$, ($np^2$)$^1D^e$, ($nd^2$)$^1G^e$, ($nf^2$)$^1I^e$,
($ng^2$)$^1K^e$, ($nh^2$)$^1M^e$ excited states of He-like ions up to
$Z$ = 12. The inadequacy of Slater's AOT for excited states of the
atomic systems is discussed. The results obtained in the present work
are in good agreement with available experimental and theoretical results.