Standard syntax?

I have been using (with success) this SQL statement in PostgreSQL:

select col1,    case when col2 = true then       col3    else       col4    end as colw,   colM
where .... etc.

The above syntax, however, does not work for Interbase (6.01). For those who
have had experience in other SQL servers, is this a "standard" or ANSI 9X
compatible syntax or should I refrain from such syntax if I want my
statements to be transportable from SQL Server to SQL Server?

Best regards,

Franz Fortuny