Problems related to attention, hyperactivity, and impulsiveness are known to impact social, academic, and vocational success. When the problems begin in childhood and lead to impaired functioning, the syndrome is identified as attention‐deficit/hyperactivity disorder (ADHD). Symptoms of the syndrome persist into adolescence and adulthood for many individuals, but less is known about characteristics of adults compared to children, especially adults attending university. Furthermore, there is little cross‐national and cross‐cultural research. This study compared DSM‐IV‐TR ADHD symptoms of US university students (N = 271) to Japanese peers (N = 712). Comparison of group means on a DSM‐IV‐TR‐based checklist indicated that Japanese students reported more problems with inattention (and overall ADHD symptoms) but not hyperactive–impulsive symptoms. Although differences were statistically significant, effect sizes were small, indicating that for practical purposes, the students reported similar levels of symptoms. Japanese students reported higher rates of meeting or exceeding symptom counts that comprise diagnostic criteria for ADHD, but differences were quite small. Using DSM‐IV‐TR thresholds, 5.70% of US students and 6.27% of Japanese students reported enough symptoms to meet the cut‐off for inattentive, hyperactive/impulsive, or combined type during childhood. With regard to recent problems, 2.66% of US students and 4.52% of Japanese students reported enough symptoms to meet the cut‐off for one of the three subtypes. Comparisons using other methods of calculating rates are also provided. This research adds to the limited knowledge of ADHD symptoms in university students across countries and it supports the view that ADHD is not merely a cultural construct. This study is among the first to identify potential attention problems in Japanese university students.