We have identified a total of 252 HII regions in NGC 7331; 44% of them are diffuse ones. The data confirm some general properties previously found in a great number of spiral galaxies; the distribution of diameters is well represented by the van den Bergh's (1981) law.
These data will be compared to a model in a very next future to study the spiral arms structure.
The data are included in the Catalogue of HII regions at the 6 m telescope (Petit 1998).
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