Antibiotic resistance is a global health concern. Although numerous strategies have tried to reduce inadequate antibiotic prescribing, antibiotics are still prescribed in 60% of acute lower respiratory tract infections (ALRTIs) cases in Catalonia (Spain). This study aims to explore service users' experiences of ALRTIs, the quality and access to healthcare services, and health education. Selective purposive sampling was carried out, based on a prior definition of participant characteristics. These were sex, age, ethnicity, date of the last ALRTI, number of ALRTIs in the last year, and treatments received. Participants with a previous diagnosis of ALRTIs were recruited from three primary health care centres in Barcelona and one in Tarragona. Twenty-nine interviews were conducted between April and June 2019. A content thematic analysis was performed. Three themes were identified: 1) risk perceptions and help-seeking; 2) treatment preferences and antibiotic use; and 3) relationship dynamics and communication with healthcare professionals. Accounts of service users' sense of autonomy towards their health and power dynamics within the healthcare system were apparent. Supporting service users to become reliable, subjective and agentic experts of their health and bodies could help them to voice their healthcare agendas. Power structures embedded within healthcare, political and economic institutions should be challenged so that healthcare services can be co-developed (with service users) and based on service users' autonomy and horizontal relationships. Special consideration should be paid to the intersection of social vulnerabilities. A concordance approach to prescribing could be key to improve the responsible use of antibiotics and to contribute to the prevention of AMR in primary healthcare. The marketisation of health, and the increased demands of private healthcare in Spain due to the financial pressures on public healthcare as a consequence of the financial crisis of 2008 and the COVID-19 pandemic, are a risk for promoting adequate antibiotic prescribing and use. Trial registration The ISAAC-CAT study has been registered in the NCT registry, ID: NCT03931577.