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+303639 and NGC6543 are presented. The extinction derived using infrared lines for BD+303639 is EB-V = 0.34, slightly higher than previous determinations. For NGC6543 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+303639 has an average T-e = 8500 K and Ne = 11 000 cm(-3). In the case of NGC6543 a T-e = 8200 K and N-e = 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.