Purpose: We aimed to investigate associations between serum levels of the advanced glycation endproduct methylglyoxal-derived hydroimidazolone (MG-H1) and retinopathy in a sample of patients with type 1 diabetes. Methods: We conducted a cross-sectional study in a Scandinavian ophthalmology outpatient clinic on 61 randomly selected patients with type 1 diabetes. Blood samples and retinal photographs were taken at the same visit. Serum levels of hydroimidazolone immunoreactivity were determined using an immunoassay, and levels of retinopathy were determined from seven standard field stereo photographs of each eye according to the ETDRS method. Results were compared between patients with and without retinopathy. Results: Hydroimidazolone quartiles were significantly associated with retinopathy (p = 0.013). The most profound increase in occurrence of retinopathy was observed from the lowest to the second-lowest hydroimidazolone quartile. Adjusted for duration of diabetes using logistic regression, a significant difference in the presence of retinopathy was found when comparing the lowest quartile with the rest (p = 0.022). Conclusions: In our patients with type 1 diabetes, serum levels of hydroimidazolone were found to be associated with retinopathy. This is in keeping with findings in a larger sample of patients with type 2 diabetes.