  We investigate the relationship between the main acceleration phase of
coronal mass ejections (CMEs) and the particle acceleration in the associated
flares as evidenced in RHESSI non-thermal X-rays for a set of 37 impulsive
flare-CME events. CME peak velocity and peak acceleration yield distinct
correlations with various parameters characterizing the flare-accelerated
electron spectra. The highest correlation coefficient is obtained for the
relation of the CME peak velocity and the total energy in accelerated electrons
(c = 0.85), supporting the idea that the acceleration of the CME and the
particle acceleration in the associated flare draw their energy from a common
source, probably magnetic reconnection in the current sheet behind the erupting
structure. In general, the CME peak velocity shows somewhat higher correlations
with the non-thermal flare parameters than the CME peak acceleration, except
for the spectral index of the accelerated electron spectrum which yields a
higher correlation with the CME peak acceleration (c = -0.6), indicating that
the hardness of the flare-accelerated electron spectrum is tightly coupled to
the impulsive acceleration process of the rising CME structure. We also
obtained high correlations between the CME initiation height $h_0$ and the
non-thermal flare parameters, with the highest correlation of $h_0$ to the
spectral index of flare-accelerated electrons (c = 0.8). This means that CMEs
erupting at low coronal heights, i.e.\ in regions of stronger magnetic fields,
are accompanied with flares which are more efficient to accelerate electrons to
high energies. In the majority of events (80%), the non-thermal flare emission
starts after the CME acceleration (6 min), giving a current sheet length at the
onset of magnetic reconnection of 21 \pm 7 Mm. The flare HXR peaks are well
synchronized with the peak of the CME acceleration profile.
