A systematic review of evidence on lags in water quality response to diffuse pollution control measures implemented in Scotland is reported. The review focused on key pollutants in catchments smaller than 300 km² in temperate regions. Findings were evaluated based on catchment typologies (e.g. catchment size, precipitation, land use, pollutant residence time, and soil /waterbody type) and data/analyses (e.g. monitoring design and record length). There was no evidence supporting fixed timeframes for a water quality response to measures or catchment typology -based lags. Observed lags varied: 1-25 years for river pollutants and potentially longer than 20 years for groundwater nitrate. Long-term water quality and catchment data are key to quantifying lags. It is recommended to keep monitoring and adjust expectations by planning for longer-term lags.