Aims.We study the photometric and structural properties of the star cluster system in the late type Sc spiral NGC 3370. Methods. BVI observations from the Advanced Camera for Surveys on board of HST are used to analyse in detail the colours, magnitudes and spatial properties of cluster candidates. The final catalogue of sources used for the study is composed by 277 objects. Results. The colour distributions of cluster candidates appear multi-modal. Although firm age constraints need the use of more age sensitive indicators, the comparison of cluster candidate colours with the colours of Galactic and Magellanic Clouds star clusters, suggests an age difference between the various sub-peaks, with a red old sub-system, a rich population of intermediate age (~1 Gyr), and a blue tail of very young (below ~100 Myr) clusters. The luminosity functions appear normal for this type of galaxy, as for the distribution of cluster effective radii (Reff). Our analysis suggests the presence of a peak in the Reff distribution at ~3.0 pc, with blue (likely young) cluster candidates showing smaller radii respect to red (likely old) objects. Finally, inspecting the properties of candidate globular clusters, we find a colour distribution matching with Galactic Globulars, with a median [Fe/H] -1.5 dex, though a non negligible tail towards lower metallicities is also present.
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