Within ten days of Catherine II's accession to the throne, she had invited Denis Diderot to come to Russia

Within ten days of Catherine II's accession to the throne, she had invited Denis Diderot to come to Russia. She even proposed that he move the publication of the "Encyclopédie", which kept running into bans in France, to Riga or Saint Petersburg. But Diderot did not take up the offer and arrived in Saint Petersburg only in October 1773. It seems that no one apart from the Empress, who made Diderot a member of the Academy, was impressed by the Frenchman. Fonvizin remarked that "the D'Alemberts and Diderots are just the same sort of charlatans as I saw every day on the boulevard."

Catherine allowed Diderot to say whatever he liked and not to stand on ceremony. He took this quite literally and, in conversation, simply banged his fist on the table, though he was also capable of seizing Catherine by the hand or slapping her on the leg. The Empress even had to place a small table between him and herself, since after such meetings she found bruises on her person.

Long before Diderot's arrival in Russia, Catherine had bought his library for fifteen thousand livres, leaving it in France for the rest of his days so that he could go on using it, had appointed him its keeper with a salary of a thousand livres a year, and when he eventually complained that his salary had gone unpaid for a year and a half, she paid him his stipend for fifty years in advance.

After his death, nearly 3,000 volumes of Diderot's library arrived in Russia. Catherine read his notebook containing his commentary on her Instruction to the deputies for the drafting of laws, and was deeply disappointed, writing: "This is sheer babble, with no knowledge of circumstances, no prudence, no foresight." After that, no mention of Diderot is to be found in Catherine's correspondence. His books did not remain in Catherine's library as a separate collection, unlike the library of Voltaire. Later, Count Dmitry Buturlin wrote that the part of the library that came from Diderot contained "not a single remarkable copy, not a single outstanding feature, and dissolved into the general mass."