In patient care and medical research patient data often has to be transferred between different electronic systems. These systems can be very heterogeneous, sometimes even legacy systems, and thus, often do not support standardized interfaces for data transfer. Since nowadays barcode scanners are commonly used in clinical routine and smartphones are accessible to most patients, we implemented different interfaces based on Data Matrix codes to transfer patient data between several medical applications. Objective of this work is to show different use cases in which Data Matrix codes have been successfully applied and discuss the lessons we have learned during the process of implementation and practical usage.