  Using a density functional method, we investigate the properties of liquid
4He droplets doped with atoms (Ne and Xe) and molecules (SF_6 and HCN). We
consider the case of droplets having a quantized vortex pinned to the dopant. A
liquid drop formula is proposed that accurately describes the total energy of
the complex and allows one to extrapolate the density functional results to
large N. For a given impurity, we find that the formation of a
dopant+vortex+4He_N complex is energetically favored below a critical size
N_cr. Our result support the possibility to observe quantized vortices in
helium droplets by means of spectroscopic techniques.
