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PAHs are the smallest components of dust. They are observed mainly near the bright UV objects heating them. Unlike large particles just a single
UV-photon is needed to heat and excite the PAHs (stochasting heating mechanism). The PAHs are concentrated generally to HII regions in spiral and irregular
galaxies. We have perfomed the aperture photometry of HII regions using infrared images from telescopes Spitzer
and Herschel at passbands 3.6, 4.5, 5.8,
8.0, 24, 70 and 160 μm. Emission of PAHs are observed at passbands 3.6 - 8.0 μm, 24 μm is emission likely of hot small particles and finally
large particles are responsible for emission at 70 and 160 μm. We determine abundances of PAHs using model of
Draine & Li (2007) . Comparing
metallicities of HII regions and abundances of PAHs we get a correlation between these parameteres. There is a lack of PAHs in low metallicity
regions, and conversely an excess of PAHs in high metallicity regions. This result is illustrated in Fig. 1. However 24 mkm emission do not
correlate with metallicity (Fig. 2). Results of this work are in this paper .
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