The study showed more than a third of schools and colleges taking the OCR exam board's syllabus opted to study Russian rulers from 1855 to 1992 - from Tsar Alexander II to Boris Yeltsin.
In this history top 10, the second most popular option was the civil rights movement in the United States.
Researchers say most schools preferred modern to medieval history.
History is one of the biggest A-level subjects - but there have been concerns it can focus too narrowly on specific eras, such as the rise of Nazism or the Tudors.
This tendency in history has been characterised as "Hitler and the Henrys".
But this study, published by the Cambridge Assessment exams group, suggests Russian history is the most popular option.
Dictatorship and Democracy in Germany, 1933-63, which includes the Nazi era, is the third most taught option - with another German history option from 1919-63, including the rise of Nazism, in eighth place.
There are three Tudor-related topic areas in the top 10 history options.
There are less popular topics, with fewer than one in 10 schools teaching the age of Gladstone and Disraeli, the German reformation and the first crusade and crusader states.
The researchers raise the question as to whether giving schools so many different options is the best way to ensure that pupils study a wide range of eras and topics.
Research co-author Simon Child said the study showed that "offering a wide range of choices does not necessarily lead to historical or geographical breadth".
Russian dictatorship is the most popular A-level history exam topic in England and Wales, research suggests.