Introduction: Inappropriate supply and an increasing demand on the healthcare system have been of concern for health policy in Germany for at least 15 years. In the primary care setting, this especially relates to an undersupply of general practitioners (GPs) in the countryside. In addition, there seem to be other regional differences, for example, a difference in accessing primary and secondary care between rural and urban areas. Despite these findings, regional differences in health services have not been studied extensively in Germany. Therefore, this study aims to explore regional variations of patient populations and reasons for accessing primary medical care. Methods and analysis: We will conduct a crosssectional observational study based on standardised interviews with 240 GPs and ∼1200 patients. Data collection started on 10 June 2015 and will probably be completed by 31 October 2016. We will include all districts and cities within 100 km from Hamburg and assign them according to the type of regions: rural, urban and environs. All eligible GPs will be invited to participate. Each practice will recruit up to 15 patients, aged 18 years or older. Questionnaires are based on a preliminary qualitative study and were pretested. Data will be analysed with descriptive statistics and regression modelling strategies adjusted for confounders and the GP-induced cluster structure. Ethics and dissemination: Our study was approved by the Ethics Committee of the Medical Association of Hamburg and is conducted in accordance with the Declaration of Helsinki. Study participants give written informed consent before data collection and data is pseudonymised. Survey data and person identifiers are stored separately in locked cabinets and have restricted availability. The results of our study will be presented at conferences and published in peer-reviewed journals.