Consent to the processing of personal data online is what drives the profit of the growing data economy. Therefore, certain websites have a strong interest in maximising user consent by optimising the design of cookie consent notices (notice) in a persuasive manner. Persuasive design uses psychological theories to influence users to make certain choices. When implemented in a way that goes against the user’s own interest this practice is known as a ‘dark pattern’. However, if implemented to promote the user’s own interests it can benefit them instead, and therefore be more likely to result in a usable (effective, efficient and satisfactory) design. This study aims to explore how persuasive design affects the usability in notices when the user goal is to decline third-party cookies.  To gain insights in respect of the above, the study was conducted in three steps: (a) the use of persuasive design through dark patterns in two different notices was examined by way of content analysis; (b) how users experienced the usability in the same notices was examined via a usability test; and (c) similarities and differences between these findings were explored through a comparative analysis. The results suggest that the mere presence of dark patterns does not determine the usability of a notice, but when they are combined in a way that affects the efficiency of the design – and therefore the cognitive load of the users – it is particularly hard for them to say no.