This research investigates and explores the influences of sales promotion on online impulse buying behaviour of consumers by comparing between the two (2) most widely used forms of sales promotion, namely, price discounts and volume discount. The aim is to identify which from is mostly preferred by online consumers and have a higher influence on impulse buying behaviour. The participants were made up of 206 online shoppers between the age of 18-35 years in Ireland, who responded to shopping scenarios that described both type of promotion. The primary data were collect using a quantitative research method and analysed employing a graphical representation method. Furthermore, the research findings indicate that online shoppers prefer price promotion over volume discount, which in turn incites a greater level of impulse buying behaviour in consumers.