Examine the motivations for new psychoactive substance (NPS) use amongst a sample of regular psychostimulant users (RPU) in Australia, and determine whether motivations differ across substances.Data were obtained from 419 RPU interviewed for the 2014 Ecstasy and related Drugs Reporting System who reported lifetime NPS use. Based on the most recent NPS used, motivations for use were rated on an 11-point scale (0 'no influence'-10 'maximum influence').For NPS overall, value for money was found to be the most highly endorsed motivation for use, scoring a median of five out of ten. However, there was substantial variation in motivations for use across substance types. Availability (i.e. no other drug was available to me at the time; 6/10) was the most highly endorsed motivation for the use of synthetic cathinones, which was significantly higher than reported for DMT. Perceived legality and availability were the most highly endorsed motivations for synthetic cannabinoids (5/10); perceived legality scored higher for synthetic cannabinoids than for all the other NPS, whilst in regards to availability synthetic cannabinoids scored significantly higher than DMT only. Value for money was the most highly endorsed motivation for NBOMe (8/10) and 2C-family substances (5/10); in regards to NBOMe this scored significantly higher than all other NPS. Short effect duration was the most highly endorsed motivation for DMT (7/10), which was significantly higher than for all other NPS.Synthetic cathinones and cannabinoids appear to be largely motivated by 'opportunistic' reasons (i.e. availability, legality), while NBOMe, 2C-family substances and DMT appear to be motivated by particular desirable qualities of a substance (i.e. value for money, short effect duration). Providing a nuanced understanding of why individuals use particular NPS improves our ability to understand the NPS phenomenon and to tailor harm reduction messages to the appropriate target groups.