**Datasets of opinion polls and surveys** are the largest and most frequently used collection of data by users from social science community. The largest part of this collection consists of data from surveys carried out by other scientists and researchers, which might be used by other users for their own **secondary analysis**. Launched in 2006 the LiDA Survey Data collection currently contains **more than 300 survey datasets** (not all datasets are available yet, as a migration project from the old infrastructure is underway for the period 2020-2024). The datasets are organised into **thematic collections** – sub-catalogues. Each survey dataset is described (documented) in **English** (see Metadata: Citation Metadata, Geospatial Metadata, Social Science and Humanities Metadata) and **Lithuanian** (see Metadata: Citation Metadata (LT), Geospatial Metadata (LT), Social Science and Humanities Metadata (LT)).