  We investigate the stellar composition of bulges and elliptical galaxies as
predicted by the CDM paradigm using semi-analytical modelling. We argue that
spheroid stars are built up of two main components, {\it merger} and {\it
quiescent}, according to the origin of the stars. The merger component is
formed during major mergers by gas driven to the centre, while the quiescent
component is formed in gaseous discs and added later to the spheroid during
major mergers. Galaxies more massive than $M_C=3 \times 10^{10}$ M$_{\odot}$
have on average only a 15% merger component in their spheroids, while smaller
galaxies can have up to 30%. The merger component increases with redshift due
to mergers involving more gas. However we do not find mergers with gas fraction
above $ \sim 40 %$ of the remnants mass. Generally the gas fraction is a
decreasing function of the redshift at which the merger occurs and the mass of
the remnant, with more massive remnants having smaller gas fraction and hence
smaller merger components. This trend is independent of the environment of the
galaxy with the only impact of the environment being that galaxies less massive
than $M_C$ have slightly larger merger components in dense environments.
  The fraction of stars in bulges for galaxies more massive than $M_C$ is
larger than 50%. We find that the majority of stars in galaxies more massive
than $M_C$ reside within bulges and ellipticals independent of redshift and
that the fraction increases with redshift. The most massive galaxies at each
redshift are elliptical galaxies.
