Abundances of Planetary Nebulae BD+30 3639 and NGC 6543

Infrared spectra taken with the Short Wavelength Spectrometer on board ISO and UV observations with IUE of planetary nebulae BD+30 3639 and NGC 6543 are presented. The extinction derived using infrared lines for BD+30 3639 is EB-V= 0.34, slightly higher than previous determinations. For NGC 6543 the extinction found from the hydrogen lines is EB-V= 0.07. Infrared, optical and ultraviolet data have been used to derive the physical parameters of the nebula. BD+30 3639 has an average Te= 8500 K and Ne=11000 cm^-3. In the case of NGC 6543 a Te = 8200 K and Ne = 5000 cm^-3 have been found, in agreement with previous determinations. The element abundances have been derived and compared to those found in the Sun and O, B stars. This comparison gives a hint of the mass of the progenitor stars from which they evolved.