Chemical vapor deposition (CVD) along with thermal decomposition of monosilane (SiH4) in a fluidized bed of multiwalled carbon nanotubes (MWCNTs) is used to prepare MWCNT-Si composites containing silicon nanoparticles deposited on the nanotube surfaces. The structure of obtained Si nanoparticles in composites based on MWCNTs with different average diameters is studied by TEM, SEM, XRD, Raman spectroscopy, and FTIR spectroscopy of diffuse reflection. The size of Si particles varies from 3 nm to 45 nm and increases together with the MWCNT diameter. The major part of precipitated silica in the nanoparticles occurs in the amorphous state with small (below 3 nm in size) inclusions of nanocrystalline silicon. Specific discharge capacity of prepared composites used as the anode material for lithium-ion batteries is estimated.