The extraction efficiency of petroleum-derived dissolved organic matter (DOM) was examined for groundwater samples from an aquifer contaminated with crude oil. Four different types of extraction were used to determine which method is best suited for the analysis of potentially toxic petroleum-derived DOM. The four types were a liquid-liquid extraction (LLE) with dichloromethane (EPA method 3510C), and three solid-phase extraction (SPE) stationary phases that are routinely used for extraction of polar analytes from water. For the LLE, that is selective for non-polar compounds, the extraction efficiency of petroleum-derived DOM decreased downgradient as the petroleum-derived DOM becomes increasingly polar due to biodegradation. In contrast, the average extraction efficiency by the SPE methods was greater than 65 % across the gradient. The results showed that SPE is more efficient for extracting petroleum-derived DOM at hydrocarbon-contaminated sites. The use of a method with greater extraction efficiency for partially-oxidized hydrocarbons may prove useful in determining relationships between their composition and structure and potential for risks to human health or the environment.